How can I deduce the hypotenuse from the information given?












4












$begingroup$


I'm going into Machine Learning and am currently brushing up on some Calculus on Coursera. Everything was going smoothly until I got to this word problem:




A ladder rests against a wall. The top of the ladder touches the wall at height $12$ meters. The length of the ladder is $4$ meters longer than the distance from the base of the ladder to the wall. Find the length of the ladder.




I am confused as to how to deduce the hypotenuse from the information given above. And have sat here trying different things with no success. What am I missing?










share|cite|improve this question











$endgroup$












  • $begingroup$
    I added the "algebra-precalculus" tag to your post. Cheers!
    $endgroup$
    – Robert Lewis
    Dec 10 '18 at 2:47










  • $begingroup$
    Draw a picture with the ladder. Label the sides of the triangle formed by the ladder, the wall, and the floor. If you call the base x, the ladder is x+4. Then use the Pythagorean theorem.
    $endgroup$
    – Joel Pereira
    Dec 10 '18 at 2:47
















4












$begingroup$


I'm going into Machine Learning and am currently brushing up on some Calculus on Coursera. Everything was going smoothly until I got to this word problem:




A ladder rests against a wall. The top of the ladder touches the wall at height $12$ meters. The length of the ladder is $4$ meters longer than the distance from the base of the ladder to the wall. Find the length of the ladder.




I am confused as to how to deduce the hypotenuse from the information given above. And have sat here trying different things with no success. What am I missing?










share|cite|improve this question











$endgroup$












  • $begingroup$
    I added the "algebra-precalculus" tag to your post. Cheers!
    $endgroup$
    – Robert Lewis
    Dec 10 '18 at 2:47










  • $begingroup$
    Draw a picture with the ladder. Label the sides of the triangle formed by the ladder, the wall, and the floor. If you call the base x, the ladder is x+4. Then use the Pythagorean theorem.
    $endgroup$
    – Joel Pereira
    Dec 10 '18 at 2:47














4












4








4


2



$begingroup$


I'm going into Machine Learning and am currently brushing up on some Calculus on Coursera. Everything was going smoothly until I got to this word problem:




A ladder rests against a wall. The top of the ladder touches the wall at height $12$ meters. The length of the ladder is $4$ meters longer than the distance from the base of the ladder to the wall. Find the length of the ladder.




I am confused as to how to deduce the hypotenuse from the information given above. And have sat here trying different things with no success. What am I missing?










share|cite|improve this question











$endgroup$




I'm going into Machine Learning and am currently brushing up on some Calculus on Coursera. Everything was going smoothly until I got to this word problem:




A ladder rests against a wall. The top of the ladder touches the wall at height $12$ meters. The length of the ladder is $4$ meters longer than the distance from the base of the ladder to the wall. Find the length of the ladder.




I am confused as to how to deduce the hypotenuse from the information given above. And have sat here trying different things with no success. What am I missing?







calculus algebra-precalculus trigonometry






share|cite|improve this question















share|cite|improve this question













share|cite|improve this question




share|cite|improve this question








edited Dec 12 '18 at 4:12









Key Flex

7,85061232




7,85061232










asked Dec 10 '18 at 2:38









Edward SeverinsenEdward Severinsen

18815




18815












  • $begingroup$
    I added the "algebra-precalculus" tag to your post. Cheers!
    $endgroup$
    – Robert Lewis
    Dec 10 '18 at 2:47










  • $begingroup$
    Draw a picture with the ladder. Label the sides of the triangle formed by the ladder, the wall, and the floor. If you call the base x, the ladder is x+4. Then use the Pythagorean theorem.
    $endgroup$
    – Joel Pereira
    Dec 10 '18 at 2:47


















  • $begingroup$
    I added the "algebra-precalculus" tag to your post. Cheers!
    $endgroup$
    – Robert Lewis
    Dec 10 '18 at 2:47










  • $begingroup$
    Draw a picture with the ladder. Label the sides of the triangle formed by the ladder, the wall, and the floor. If you call the base x, the ladder is x+4. Then use the Pythagorean theorem.
    $endgroup$
    – Joel Pereira
    Dec 10 '18 at 2:47
















$begingroup$
I added the "algebra-precalculus" tag to your post. Cheers!
$endgroup$
– Robert Lewis
Dec 10 '18 at 2:47




$begingroup$
I added the "algebra-precalculus" tag to your post. Cheers!
$endgroup$
– Robert Lewis
Dec 10 '18 at 2:47












$begingroup$
Draw a picture with the ladder. Label the sides of the triangle formed by the ladder, the wall, and the floor. If you call the base x, the ladder is x+4. Then use the Pythagorean theorem.
$endgroup$
– Joel Pereira
Dec 10 '18 at 2:47




$begingroup$
Draw a picture with the ladder. Label the sides of the triangle formed by the ladder, the wall, and the floor. If you call the base x, the ladder is x+4. Then use the Pythagorean theorem.
$endgroup$
– Joel Pereira
Dec 10 '18 at 2:47










2 Answers
2






active

oldest

votes


















6












$begingroup$

Let $d$ be the distance from the ladder to the wall, and $l$ the length of the ladder.
Then



$l = d + 4; tag 1$



since the wall is mos' likely perpendicular to the ground, we may deploy the Pythagorean theorem and write



$l^2 = (12)^2 + d^2; tag 2$



substituting (1) into (2) yields



$(d + 4)^2 = 144 + d^2, tag 3$



$d^2 + 8d + 16 = 144 + d^2, tag 4$



$8d + 16 = 144 Longrightarrow 8d = 128 Longrightarrow d = 16M Longrightarrow l = 20M. tag 5$






share|cite|improve this answer









$endgroup$









  • 2




    $begingroup$
    Oh my. I distributed the 2 exponent to d and 4 individually instead of multiplying the expression by itself. Not the first time this has gotten me.
    $endgroup$
    – Edward Severinsen
    Dec 10 '18 at 2:49






  • 1




    $begingroup$
    @EdwardSeverinsen: we're all learners, my friend!
    $endgroup$
    – Robert Lewis
    Dec 10 '18 at 2:50






  • 6




    $begingroup$
    No, the answer should be "at that angle, the ladder doesn't rest at the wall" ;-)
    $endgroup$
    – DonQuiKong
    Dec 10 '18 at 9:51






  • 1




    $begingroup$
    @DonQuiKong I wouldn't get on it, that's for sure!
    $endgroup$
    – JTPenguin
    Dec 10 '18 at 11:48



















13












$begingroup$

enter image description here



Given the length of the wall as $12$.



Take the length of the base as $x$.



Since the length of the ladder $l$ is $4$ meters greater than the base, we have $l = x+4$



Now according to the pythagorean theorem we have,



$begin{align}
(x+4)^2 &= 12^2 + x^2 \
x^2 + 16 + 8x &= 144 + x^2 \
8x &= 128 \
x & = 16
end{align}$



So, the length of the ladder $l = x+4 = 16+4 = 20$






share|cite|improve this answer











$endgroup$









  • 4




    $begingroup$
    Nice graphic, +1!
    $endgroup$
    – Robert Lewis
    Dec 10 '18 at 2:52






  • 2




    $begingroup$
    @RobertLewis Thanks!
    $endgroup$
    – Key Flex
    Dec 10 '18 at 2:57






  • 1




    $begingroup$
    Just as a note 4 times greater than the base is ambiguous and could imply it is x * 4 and not x + 4.
    $endgroup$
    – Felix Guo
    Dec 10 '18 at 7:36






  • 2




    $begingroup$
    @FelixGuo "4 times greater" isn't ambiguous at all: it can only mean $xtimes 4$ and never $x+4$. It was just a mistake, which has now been corrected.
    $endgroup$
    – David Richerby
    Dec 10 '18 at 14:47











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2 Answers
2






active

oldest

votes








2 Answers
2






active

oldest

votes









active

oldest

votes






active

oldest

votes









6












$begingroup$

Let $d$ be the distance from the ladder to the wall, and $l$ the length of the ladder.
Then



$l = d + 4; tag 1$



since the wall is mos' likely perpendicular to the ground, we may deploy the Pythagorean theorem and write



$l^2 = (12)^2 + d^2; tag 2$



substituting (1) into (2) yields



$(d + 4)^2 = 144 + d^2, tag 3$



$d^2 + 8d + 16 = 144 + d^2, tag 4$



$8d + 16 = 144 Longrightarrow 8d = 128 Longrightarrow d = 16M Longrightarrow l = 20M. tag 5$






share|cite|improve this answer









$endgroup$









  • 2




    $begingroup$
    Oh my. I distributed the 2 exponent to d and 4 individually instead of multiplying the expression by itself. Not the first time this has gotten me.
    $endgroup$
    – Edward Severinsen
    Dec 10 '18 at 2:49






  • 1




    $begingroup$
    @EdwardSeverinsen: we're all learners, my friend!
    $endgroup$
    – Robert Lewis
    Dec 10 '18 at 2:50






  • 6




    $begingroup$
    No, the answer should be "at that angle, the ladder doesn't rest at the wall" ;-)
    $endgroup$
    – DonQuiKong
    Dec 10 '18 at 9:51






  • 1




    $begingroup$
    @DonQuiKong I wouldn't get on it, that's for sure!
    $endgroup$
    – JTPenguin
    Dec 10 '18 at 11:48
















6












$begingroup$

Let $d$ be the distance from the ladder to the wall, and $l$ the length of the ladder.
Then



$l = d + 4; tag 1$



since the wall is mos' likely perpendicular to the ground, we may deploy the Pythagorean theorem and write



$l^2 = (12)^2 + d^2; tag 2$



substituting (1) into (2) yields



$(d + 4)^2 = 144 + d^2, tag 3$



$d^2 + 8d + 16 = 144 + d^2, tag 4$



$8d + 16 = 144 Longrightarrow 8d = 128 Longrightarrow d = 16M Longrightarrow l = 20M. tag 5$






share|cite|improve this answer









$endgroup$









  • 2




    $begingroup$
    Oh my. I distributed the 2 exponent to d and 4 individually instead of multiplying the expression by itself. Not the first time this has gotten me.
    $endgroup$
    – Edward Severinsen
    Dec 10 '18 at 2:49






  • 1




    $begingroup$
    @EdwardSeverinsen: we're all learners, my friend!
    $endgroup$
    – Robert Lewis
    Dec 10 '18 at 2:50






  • 6




    $begingroup$
    No, the answer should be "at that angle, the ladder doesn't rest at the wall" ;-)
    $endgroup$
    – DonQuiKong
    Dec 10 '18 at 9:51






  • 1




    $begingroup$
    @DonQuiKong I wouldn't get on it, that's for sure!
    $endgroup$
    – JTPenguin
    Dec 10 '18 at 11:48














6












6








6





$begingroup$

Let $d$ be the distance from the ladder to the wall, and $l$ the length of the ladder.
Then



$l = d + 4; tag 1$



since the wall is mos' likely perpendicular to the ground, we may deploy the Pythagorean theorem and write



$l^2 = (12)^2 + d^2; tag 2$



substituting (1) into (2) yields



$(d + 4)^2 = 144 + d^2, tag 3$



$d^2 + 8d + 16 = 144 + d^2, tag 4$



$8d + 16 = 144 Longrightarrow 8d = 128 Longrightarrow d = 16M Longrightarrow l = 20M. tag 5$






share|cite|improve this answer









$endgroup$



Let $d$ be the distance from the ladder to the wall, and $l$ the length of the ladder.
Then



$l = d + 4; tag 1$



since the wall is mos' likely perpendicular to the ground, we may deploy the Pythagorean theorem and write



$l^2 = (12)^2 + d^2; tag 2$



substituting (1) into (2) yields



$(d + 4)^2 = 144 + d^2, tag 3$



$d^2 + 8d + 16 = 144 + d^2, tag 4$



$8d + 16 = 144 Longrightarrow 8d = 128 Longrightarrow d = 16M Longrightarrow l = 20M. tag 5$







share|cite|improve this answer












share|cite|improve this answer



share|cite|improve this answer










answered Dec 10 '18 at 2:46









Robert LewisRobert Lewis

45.4k23065




45.4k23065








  • 2




    $begingroup$
    Oh my. I distributed the 2 exponent to d and 4 individually instead of multiplying the expression by itself. Not the first time this has gotten me.
    $endgroup$
    – Edward Severinsen
    Dec 10 '18 at 2:49






  • 1




    $begingroup$
    @EdwardSeverinsen: we're all learners, my friend!
    $endgroup$
    – Robert Lewis
    Dec 10 '18 at 2:50






  • 6




    $begingroup$
    No, the answer should be "at that angle, the ladder doesn't rest at the wall" ;-)
    $endgroup$
    – DonQuiKong
    Dec 10 '18 at 9:51






  • 1




    $begingroup$
    @DonQuiKong I wouldn't get on it, that's for sure!
    $endgroup$
    – JTPenguin
    Dec 10 '18 at 11:48














  • 2




    $begingroup$
    Oh my. I distributed the 2 exponent to d and 4 individually instead of multiplying the expression by itself. Not the first time this has gotten me.
    $endgroup$
    – Edward Severinsen
    Dec 10 '18 at 2:49






  • 1




    $begingroup$
    @EdwardSeverinsen: we're all learners, my friend!
    $endgroup$
    – Robert Lewis
    Dec 10 '18 at 2:50






  • 6




    $begingroup$
    No, the answer should be "at that angle, the ladder doesn't rest at the wall" ;-)
    $endgroup$
    – DonQuiKong
    Dec 10 '18 at 9:51






  • 1




    $begingroup$
    @DonQuiKong I wouldn't get on it, that's for sure!
    $endgroup$
    – JTPenguin
    Dec 10 '18 at 11:48








2




2




$begingroup$
Oh my. I distributed the 2 exponent to d and 4 individually instead of multiplying the expression by itself. Not the first time this has gotten me.
$endgroup$
– Edward Severinsen
Dec 10 '18 at 2:49




$begingroup$
Oh my. I distributed the 2 exponent to d and 4 individually instead of multiplying the expression by itself. Not the first time this has gotten me.
$endgroup$
– Edward Severinsen
Dec 10 '18 at 2:49




1




1




$begingroup$
@EdwardSeverinsen: we're all learners, my friend!
$endgroup$
– Robert Lewis
Dec 10 '18 at 2:50




$begingroup$
@EdwardSeverinsen: we're all learners, my friend!
$endgroup$
– Robert Lewis
Dec 10 '18 at 2:50




6




6




$begingroup$
No, the answer should be "at that angle, the ladder doesn't rest at the wall" ;-)
$endgroup$
– DonQuiKong
Dec 10 '18 at 9:51




$begingroup$
No, the answer should be "at that angle, the ladder doesn't rest at the wall" ;-)
$endgroup$
– DonQuiKong
Dec 10 '18 at 9:51




1




1




$begingroup$
@DonQuiKong I wouldn't get on it, that's for sure!
$endgroup$
– JTPenguin
Dec 10 '18 at 11:48




$begingroup$
@DonQuiKong I wouldn't get on it, that's for sure!
$endgroup$
– JTPenguin
Dec 10 '18 at 11:48











13












$begingroup$

enter image description here



Given the length of the wall as $12$.



Take the length of the base as $x$.



Since the length of the ladder $l$ is $4$ meters greater than the base, we have $l = x+4$



Now according to the pythagorean theorem we have,



$begin{align}
(x+4)^2 &= 12^2 + x^2 \
x^2 + 16 + 8x &= 144 + x^2 \
8x &= 128 \
x & = 16
end{align}$



So, the length of the ladder $l = x+4 = 16+4 = 20$






share|cite|improve this answer











$endgroup$









  • 4




    $begingroup$
    Nice graphic, +1!
    $endgroup$
    – Robert Lewis
    Dec 10 '18 at 2:52






  • 2




    $begingroup$
    @RobertLewis Thanks!
    $endgroup$
    – Key Flex
    Dec 10 '18 at 2:57






  • 1




    $begingroup$
    Just as a note 4 times greater than the base is ambiguous and could imply it is x * 4 and not x + 4.
    $endgroup$
    – Felix Guo
    Dec 10 '18 at 7:36






  • 2




    $begingroup$
    @FelixGuo "4 times greater" isn't ambiguous at all: it can only mean $xtimes 4$ and never $x+4$. It was just a mistake, which has now been corrected.
    $endgroup$
    – David Richerby
    Dec 10 '18 at 14:47
















13












$begingroup$

enter image description here



Given the length of the wall as $12$.



Take the length of the base as $x$.



Since the length of the ladder $l$ is $4$ meters greater than the base, we have $l = x+4$



Now according to the pythagorean theorem we have,



$begin{align}
(x+4)^2 &= 12^2 + x^2 \
x^2 + 16 + 8x &= 144 + x^2 \
8x &= 128 \
x & = 16
end{align}$



So, the length of the ladder $l = x+4 = 16+4 = 20$






share|cite|improve this answer











$endgroup$









  • 4




    $begingroup$
    Nice graphic, +1!
    $endgroup$
    – Robert Lewis
    Dec 10 '18 at 2:52






  • 2




    $begingroup$
    @RobertLewis Thanks!
    $endgroup$
    – Key Flex
    Dec 10 '18 at 2:57






  • 1




    $begingroup$
    Just as a note 4 times greater than the base is ambiguous and could imply it is x * 4 and not x + 4.
    $endgroup$
    – Felix Guo
    Dec 10 '18 at 7:36






  • 2




    $begingroup$
    @FelixGuo "4 times greater" isn't ambiguous at all: it can only mean $xtimes 4$ and never $x+4$. It was just a mistake, which has now been corrected.
    $endgroup$
    – David Richerby
    Dec 10 '18 at 14:47














13












13








13





$begingroup$

enter image description here



Given the length of the wall as $12$.



Take the length of the base as $x$.



Since the length of the ladder $l$ is $4$ meters greater than the base, we have $l = x+4$



Now according to the pythagorean theorem we have,



$begin{align}
(x+4)^2 &= 12^2 + x^2 \
x^2 + 16 + 8x &= 144 + x^2 \
8x &= 128 \
x & = 16
end{align}$



So, the length of the ladder $l = x+4 = 16+4 = 20$






share|cite|improve this answer











$endgroup$



enter image description here



Given the length of the wall as $12$.



Take the length of the base as $x$.



Since the length of the ladder $l$ is $4$ meters greater than the base, we have $l = x+4$



Now according to the pythagorean theorem we have,



$begin{align}
(x+4)^2 &= 12^2 + x^2 \
x^2 + 16 + 8x &= 144 + x^2 \
8x &= 128 \
x & = 16
end{align}$



So, the length of the ladder $l = x+4 = 16+4 = 20$







share|cite|improve this answer














share|cite|improve this answer



share|cite|improve this answer








edited Dec 10 '18 at 8:17









SQB

1,74611026




1,74611026










answered Dec 10 '18 at 2:49









Key FlexKey Flex

7,85061232




7,85061232








  • 4




    $begingroup$
    Nice graphic, +1!
    $endgroup$
    – Robert Lewis
    Dec 10 '18 at 2:52






  • 2




    $begingroup$
    @RobertLewis Thanks!
    $endgroup$
    – Key Flex
    Dec 10 '18 at 2:57






  • 1




    $begingroup$
    Just as a note 4 times greater than the base is ambiguous and could imply it is x * 4 and not x + 4.
    $endgroup$
    – Felix Guo
    Dec 10 '18 at 7:36






  • 2




    $begingroup$
    @FelixGuo "4 times greater" isn't ambiguous at all: it can only mean $xtimes 4$ and never $x+4$. It was just a mistake, which has now been corrected.
    $endgroup$
    – David Richerby
    Dec 10 '18 at 14:47














  • 4




    $begingroup$
    Nice graphic, +1!
    $endgroup$
    – Robert Lewis
    Dec 10 '18 at 2:52






  • 2




    $begingroup$
    @RobertLewis Thanks!
    $endgroup$
    – Key Flex
    Dec 10 '18 at 2:57






  • 1




    $begingroup$
    Just as a note 4 times greater than the base is ambiguous and could imply it is x * 4 and not x + 4.
    $endgroup$
    – Felix Guo
    Dec 10 '18 at 7:36






  • 2




    $begingroup$
    @FelixGuo "4 times greater" isn't ambiguous at all: it can only mean $xtimes 4$ and never $x+4$. It was just a mistake, which has now been corrected.
    $endgroup$
    – David Richerby
    Dec 10 '18 at 14:47








4




4




$begingroup$
Nice graphic, +1!
$endgroup$
– Robert Lewis
Dec 10 '18 at 2:52




$begingroup$
Nice graphic, +1!
$endgroup$
– Robert Lewis
Dec 10 '18 at 2:52




2




2




$begingroup$
@RobertLewis Thanks!
$endgroup$
– Key Flex
Dec 10 '18 at 2:57




$begingroup$
@RobertLewis Thanks!
$endgroup$
– Key Flex
Dec 10 '18 at 2:57




1




1




$begingroup$
Just as a note 4 times greater than the base is ambiguous and could imply it is x * 4 and not x + 4.
$endgroup$
– Felix Guo
Dec 10 '18 at 7:36




$begingroup$
Just as a note 4 times greater than the base is ambiguous and could imply it is x * 4 and not x + 4.
$endgroup$
– Felix Guo
Dec 10 '18 at 7:36




2




2




$begingroup$
@FelixGuo "4 times greater" isn't ambiguous at all: it can only mean $xtimes 4$ and never $x+4$. It was just a mistake, which has now been corrected.
$endgroup$
– David Richerby
Dec 10 '18 at 14:47




$begingroup$
@FelixGuo "4 times greater" isn't ambiguous at all: it can only mean $xtimes 4$ and never $x+4$. It was just a mistake, which has now been corrected.
$endgroup$
– David Richerby
Dec 10 '18 at 14:47


















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