# Calling people who like to do maths!?

We have never been taught this and we have to finish the paper. Help appreciated! 😊

Its pythagoras btw

### 15 Answers

- jeffrcalLv 79 months ago
It is Pythagoras. How do you know that if you weren't taught?

13^2 + x^2 = 18^2

solving for x I get x^2 = 18^2 - 13^2 =155

so x = 12.4

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- 9 months ago
hehe I love non-americans and saying maths, and b/c you asked very nicely

Pythagoras is a^2 + b^2 = c^2 where c is the hypotenuse and a and b are the legs of a right triangle. the hypotenuse is the long side and a and b are the shorter sides.

so your x is a leg, let's call it b.

a^2 + b^2 = c^2

13^2 + b^2 = 18^2

b^2 = 18^2 - 13^2

b = sqrt(18^2 - 13^2)

plug that sucker in! and according to this other guy, it's 12.4

- ignoramusLv 79 months ago
I presume that YOU do not "like to do math". I do not believe that you have not been taught how to use the Pythagoras theorem.

- Ian HLv 79 months ago
You probably have been taught the Pythagorean Theorem but perhaps you forgot about it or it did not make a big impression or maybe you feel unsure about it. This problem is easier than you think. Difference of two squares.

x^2 = 18^2 – 13^2 = (18 – 13) * (18 + 13) = 5*31 = 155

Using a calculator, x = √(155) ~ 12.4498995 .....

That is just below 12.45 so, to 3 significant figures x ~ 12.4

- PuzzlingLv 79 months ago
You really haven't been taught the Pythagorean Theorem? You aren't familiar with:

a² + b² = c²

a and b are the lengths of the legs of the right triangle.

c is the hypotenuse.

In your case:

a = x

b = 13

c = 18

So write:

x² + 13² = 18²

x² + 169 = 324

x² = 324 - 169

x² = 155

x = √155

It seems they want an approximate answer and if we round to 3 significant figures, that is 12.4 cm.

Source(s): https://www.mathsisfun.com/pythagoras.html - llafferLv 79 months ago
Since you know this is a right triangle, you can use Pythagorean Theorem to solve for an unknown side given that you know the other two:

a² + b² = c²

13² + x² = 18²

169 + x² = 324

x² = 155

x = 12.5 cm (rounded to 3SF)