Question

If the mean of A and B is 20, the mean of B and C is 24 and the mean of A,B and C is 18.What is the mean of A and C?

Answer 1

Answer:

the mean of A and C is 10

Step-by-step explanation:

Given;

mean of A and B = 20

mean of B and C = 24

mean of A, B and C = 18

$\frac{A + B}{2} = 20\\\\A+ B = 40 ---- (1)\\\\\frac{B + C}{2} = 24\\\\B+ C = 48----(2)\\\\\frac{A+ B+ C}{3} = 18\\\\A+ B+ C= 54---(3)\\\\From (1); \ A = 40 - B\\\\From(2); \ C = 48 - B\\\\\Substitute \ the \ values \ of \ A \ and \ C \ into \ (3)\\\\(40-B) + B + (48-B) = 54\\\\simplify;\\\\(40 + 48) + (B-B-B)= 54\\\\88 -B = 54\\\\-B = 54-88\\\\-B = -34\\\\B = 34$

Recall; A = 40 - B

           A = 40 - 34

           A = 6

Also, C = 48 - B

        C = 48 - 34

       C = 14

Therefore, the mean of A and C is calculated as;

$= \frac{A + C}{2} \\\\= \frac{6 + 14}{2} \\\\= 10$