Question

The average of nine numbers is 60, that of the first five numbers is 55 and the next three is 65. The ninth number is 10 less than the tenth number. Then, tenth number is :

• A. 80
• B. 70
• C. 75
• D. 85

Answer 1

Answer:

A. 80

The sum of nine numbers = 60 × 9 = 540 The sum of the first five numbers = 55 × 5 = 275 The sum of the next three numbers = 65 × 3 = 195 Ninth number = (540 – 275 – 195) = (540 – 470) = 70 Tenth number = 70 + 10 = 80