Question

A, B and C stand for 3 different numbers.

The mean of A and B is 40.
The mean of B and C is 35

A+B+ C

Calculate ALL their values.

Answer 1

Mean of A & B : (A+B)/2 = 40. Cross multiply
A + B = 80.

Mean of B & C: (B+C)/2 = 35. Cross multiply
B + C = 70.

(A + B + C) = 100 Note A + B = 80.

Therefore C = 100 - (A+B) = 100 - 80 = 20.
C = 20.

A = 100 - (B+C) = 100 - 70 = 30.
A = 30.

A + B = 80
30 + B = 80
B = 80 -30 = 50.

A = 30, B = 50, C = 20.

Answer 2

The mean is x amount of numbers added together divided by x. Since both mean questions have only 2 numbers, you times 40 and 35 by 2 to reverse the question.

40 X 2 = 80 = a + b.
35 X 2 = 70 = b + c.
100 = a + b + c

80 and 70 are quite close together. Therefore, b would probably be around 40 - 60. I used trial and error to work out the answer.

b = 40
80 - 40 = 40.
a = 40.
70 - 40 = 30.
c = 30.
40 + 40 + 30 = 110.
THIS ANSWER IS WRONG.

b = 50.
80 - 50 = 30.
a = 30.
70 - 50 = 20.
c = 20.
50 + 30 + 20 = 100.
THIS ANSWER IS CORRECT.

a = 30
b = 50
c = 20