Question

The mean of a certain number of observations is $40$. If two or more items with values $50$ and $64$ are added to this data, the mean rises to $42$. Find the number of items in the original data.

• A. $14$
• B. $15$
• C. $16$
• D. $17$

Answer 1

The correct option is B $15$

Current mean
$\frac{40x}{x}=40$
New mean:
$\frac{40x+50+64}{x+2}$
$40x+114=42x+84$
$30=2x$
$x=30/2$
$x=15$.