Question

The mean of two number is 13. If one of them is 20, find out the other

Answer 1

Given

The mean of two numbers is 13

one number is 20

To Find

the other number

$\sf\huge\bold{\underline{\underline{{Solution}}}}$

Formula for finding mean:

$\sf \boxed{\bold{Mean = \dfrac{sum \: of \: the \: terms}{no.of \:terms }} }$

Let the second number be 'x'

According to the question

There are two terms or numbers say 23 and x

and no.of terms is 2

$\sf \: Mean = \dfrac{23 + x}{2}$

$\sf \longmapsto20 = \dfrac{23 + x}{2}$

Cross multiply to both sides :

$\sf \longmapsto23 + x = 20 \times 2$

$\sf \longmapsto23 + x = 40$

$\sf \longmapsto \: x = 40 - 23$

$\sf \longmapsto \: x = 17$

$\sf \bold{x = 17}$

∴The other number is 17

Check:-

Mean =23+17/2

Mean=40/2

Mean=20