Question

The average of five numbers a, b, c, d and e is 17.2. The average of the numbers b, c and d is 15. If a is equal to 10, find the number e.

• A. 51
• B. 41
• C. 21
• D. 31

Answer 1

Answer:

D. 31

Solution: Given: The average of five numbers a, b, c, d and e = 17.2 The average of the numbers b, c and d is 15 a = 10 Formula: Average of n numbers a1, a2, ..., an = (a1 + a2 + ... + an)/n Calculation: (a + b + c + d + e)/5 = 17.2 ⇒ a + b + c + d + e = 5 × 17.2 = 86 (b + c + d)/3 = 15 ⇒ b + c + d = 45 a = 10 a + b + c + d + e = 86 ⇒ 10 + 45 + e = 86 e = 86 – 55 = 31