Question 90

The average of two numbers A and B is 20, that of B and C is 19 and of C and A it is 21. What is the value of A?

Solution

average of two numbers A and B is 20

sum of two numbers A and B = $$ 20 \times 2 = 40 $$

average of two numbers B and C is 19

sum of two numbers B and C = $$ 19 \times 2 = 38 $$

average of two numbers C and A is 21

sum of two numbers C and A = $$ 21 \times 2 = 42 $$

2(A + B + C) = 120

A + B + C = 60

A = 60 - 38 = 22

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