The average of 5 numbers is 72. The average of the first three is 70, and the last three is 75. What is the third number?
Show answer & explanation
Correct answer: B
Explanation
Total sum of 5 numbers = 72 × 5 = 360
Sum of the first 3 numbers = 70 × 3 = 210
Sum of the last 3 numbers = 75 × 3 = 225
Sum of the first 3 and last 3 numbers = 210 + 225 = 435
Third number = 435 - 360 = 75