Question

a+b=5 a+b=7.5 c+a=8.5 average

Answer 1

We have been given three equations which are

a+b=5

b+c=7.5

c+a=8.5

Now question says to find their mean.

We know that mean is of any set of numbers say {x,y,z} is found by adding those numbers then divide by total numbers.

Like mean of {x,y,z} is given by (x+y+z)/3.

If you carefully look at given equations, each letter a, b and c appears twice .

So that means total number of participants =6

Now plug those values into formula of mean we get:

$Mean= \frac{(a+b)+(b+c)+(c+a)}{6}$

plug values from given equations.

$Mean= \frac{(5)+(7.5)+(8.5)}{6}$

$Mean= \frac{21}{6}$

$Mean= 3.5$

Hence correct choice is C) 3.5.