How can I deduce the hypotenuse from the information given?
$begingroup$
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?
calculus algebra-precalculus trigonometry
$endgroup$
add a comment |
$begingroup$
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?
calculus algebra-precalculus trigonometry
$endgroup$
$begingroup$
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
add a comment |
$begingroup$
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?
calculus algebra-precalculus trigonometry
$endgroup$
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
calculus algebra-precalculus trigonometry
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
add a comment |
$begingroup$
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
add a comment |
2 Answers
2
active
oldest
votes
$begingroup$
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
$(d + 4)^2 = 144 + d^2, tag 3$
$d^2 + 8d + 16 = 144 + d^2, tag 4$
$8d + 16 = 144 Longrightarrow 8d = 128 Longrightarrow d = 16M Longrightarrow l = 20M. tag 5$
$endgroup$
2
$begingroup$
Oh my. I distributed the 2 exponent tod
and4
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
add a comment |
$begingroup$
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 $l = x+4 = 16+4 = 20$
$endgroup$
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 note4 times greater than the base
is ambiguous and could imply it isx * 4
and notx + 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
add a comment |
Your Answer
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2 Answers
2
active
oldest
votes
2 Answers
2
active
oldest
votes
active
oldest
votes
active
oldest
votes
$begingroup$
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
$(d + 4)^2 = 144 + d^2, tag 3$
$d^2 + 8d + 16 = 144 + d^2, tag 4$
$8d + 16 = 144 Longrightarrow 8d = 128 Longrightarrow d = 16M Longrightarrow l = 20M. tag 5$
$endgroup$
2
$begingroup$
Oh my. I distributed the 2 exponent tod
and4
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
add a comment |
$begingroup$
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
$(d + 4)^2 = 144 + d^2, tag 3$
$d^2 + 8d + 16 = 144 + d^2, tag 4$
$8d + 16 = 144 Longrightarrow 8d = 128 Longrightarrow d = 16M Longrightarrow l = 20M. tag 5$
$endgroup$
2
$begingroup$
Oh my. I distributed the 2 exponent tod
and4
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
add a comment |
$begingroup$
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
$(d + 4)^2 = 144 + d^2, tag 3$
$d^2 + 8d + 16 = 144 + d^2, tag 4$
$8d + 16 = 144 Longrightarrow 8d = 128 Longrightarrow d = 16M Longrightarrow l = 20M. tag 5$
$endgroup$
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
$(d + 4)^2 = 144 + d^2, tag 3$
$d^2 + 8d + 16 = 144 + d^2, tag 4$
$8d + 16 = 144 Longrightarrow 8d = 128 Longrightarrow d = 16M Longrightarrow l = 20M. tag 5$
answered Dec 10 '18 at 2:46
Robert LewisRobert Lewis
45.4k23065
45.4k23065
2
$begingroup$
Oh my. I distributed the 2 exponent tod
and4
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
add a comment |
2
$begingroup$
Oh my. I distributed the 2 exponent tod
and4
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
add a comment |
$begingroup$
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 $l = x+4 = 16+4 = 20$
$endgroup$
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 note4 times greater than the base
is ambiguous and could imply it isx * 4
and notx + 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
add a comment |
$begingroup$
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 $l = x+4 = 16+4 = 20$
$endgroup$
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 note4 times greater than the base
is ambiguous and could imply it isx * 4
and notx + 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
add a comment |
$begingroup$
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 $l = x+4 = 16+4 = 20$
$endgroup$
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 $l = x+4 = 16+4 = 20$
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 note4 times greater than the base
is ambiguous and could imply it isx * 4
and notx + 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
add a comment |
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 note4 times greater than the base
is ambiguous and could imply it isx * 4
and notx + 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
add a comment |
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$begingroup$
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