Question

a group of 3 numbers has an average of 17. the first two numbers are 12 and 19. what is the third number? a. 17 b. 19 c. 20 d. 23 e. 30

Answer 1

c. 20

Explanation:

The average of 3 numbers is the sum of the three numbers divided by 3.

Let the unknown number be x.

(12 + 19 + x)/3 = 17

Multiply both sides by 3.

12 + 19 + x = 51

Add 12 and 19.

31 + x = 51

Subtract 31 from both sides.

x = 20

Answer: c. 20