Question

There are four different numbers. The average of the first three numbers is three times the fourth number, and the average of all the four numbers is 55. What is the sum of the first three numbers?

• A. 172
• B. 165
• C. 153
• D. 198

Answer 1

Answer:

D. 198

Average of all the four numbers = 55 Average of the first three numbers = 3 × Fourth number Let the fourth number be = n Average of first 3 numbers = 3n Sum of first three numbers = 3 × 3n = 9n Average of 4 numbers = 55 Sum of 4 numbers = 55 × 4 = 220 9n+ n = 220 10n = 220 n = 22 The sum of the first 3 numbers = 9n = 9 × 22 = 198