Question

The mean weight of a group of 10 items is 28 and that of another group of n items is 35. The mean of combined group of 10 + n items is found to be 30. The value of n is

• A. 2
• B. 4
• C. 10
• D. 12

Answer 1

Answer: (B)

4

Answer 2

Combined mean $= \frac{10 \times 28 + 35 \times n}{10 + n}$ $\Rightarrow \, 30 = \frac{280 + 35n}{10 + n}$ $\Rightarrow \, 300 + 30n = 280 + 35n$ $\Rightarrow \, 5n = 20 \Rightarrow n = 4$