Question

If each of 'n' readings are increased by 5, then the arithmetic mean of new 'n' readings is equal to 10. If each of the original readings are multiplied by 3, then the arithmetic mean of new readings will be

• A. 5
• B. 10
• C. 15
• D. 20

Answer 1

The correct option is C 15

Let original sumof numbers $=S$

$\frac{S+5n}{n}=10$

$\Rightarrow S=5n$

$\Rightarrow \frac{3S}{n}=\frac{3\times 5n}{n}=15$