In the formula x̄ = a + h $\Big(\dfrac{\Sigma f$i ui}{\Sigma f_i}\Big) for finding the mean of grouped frequency distribution, u_i =

1. $\Big(\dfrac{x_i + a}{h}\Big)$

2. h (x_i − a)

3. $\Big(\dfrac{x_i − a}{h}\Big)$

4. $\Big(\dfrac{a − x_i}{h}\Big)$

In a class of 100 students, the mean marks obtained in a certain test is 30 and in another class of 50 students the mean marks obtained in the same test is 60. The mean marks obtained by the students of both the classes taken together is :

1. 40

2. 45

3. 48

4. 50

The combined mean of three groups is 12 and the combined mean of first two groups is 3. If the first, second and third groups have 2, 3 and 5 items respectively, then the mean of third group is :

1. 10

2. 12

3. 13

4. 21

The mean weight of 17 boxes is 92 kg. If 18 new boxes are added, the mean weight increases by 3 kg. What will be the mean weight of the 18 new boxes?

1. 91.8 kg

2. 92.8 kg

3. 97.8 kg

4. 98.8 kg