Exams › IBPS PO › Quantitative Aptitude

If the average of seven numbers is 24 and the average of the first six numbers is 21, then if the last number is doubled, what is the new average?

1. 44
2. 30
3. 34
4. 56

Correct answer: 30

Solution

The sum of seven numbers is $7\times 24=168$. The sum of the first six numbers is $6\times 21=126$, so the seventh number is $168-126=42$. Doubling it adds 42 more, making the new sum 210, and the new average is $210/7=30$.

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