Multiple choice

The average of 5 numbers is 65. The average of the first two numbers is 81 and the average of the last two numbers is 38. What is the third number?

  1. 63

  2. 87

  3. 99

  4. 54

Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation

The average of 5 numbers is 65, so their sum is 5 × 65 = 325. The first two numbers average to 81, so their sum is 2 × 81 = 162. The last two numbers average to 38, so their sum is 2 × 38 = 76. Therefore, the third number = Total sum - (Sum of first two + Sum of last two) = 325 - (162 + 76) = 325 - 238 = 87.