Question

Average of 40 numbers is 71. If the number 100 replaced by 140, then average is increased by.

• A. 3
• B. 4
• C. 2
• D. 1

Answer 1

Answer:

D. 1

Solution: Given: Average of 40 numbers = 71 Formula: Average = Sum of all observations/Total number of all observations Calculation: Sum of 40 numbers = 40 × 71 = 2840 New sum of 40 numbers = 2840 – 100 + 140 = 2880 New average of 40 numbers = 2880/40 = 72 ∴ The average increased = 72 – 71 = 1 Shortcut Trick: New average = Old average + (Change in number/Total numbers) New average of 40 numbers = 71 + (140 – 100)/40 = 71 + 1 = 72 ∴ The average increased = 72 – 71 = 1