A distribution consists of three groups having 40, 50 and 60 item. The means of the group are 20,26 and 15 respectively, What will be the mean of the distribution ?

The correct answer is (c) 25.

The mean of a distribution is the sum of the values in the distribution divided by the number of values. In this case, the distribution consists of three groups with 40, 50, and 60 items, respectively. The means of the groups are 20, 26, and 15, respectively. Therefore, the sum of the values in the distribution is $40 \times 20 + 50 \times 26 + 60 \times 15 = 2400$. The number of values in the distribution is $40 + 50 + 60 = 150$. Therefore, the mean of the distribution is $\frac{2400}{150} = 25$.

Option (a) is incorrect because it is the mean of the first group only. Option (b) is incorrect because it is the mean of the second group only. Option (d) is incorrect because it is the mean of the third group only.