The width of each of 5 continuous classes in a frequency distribution is 5 and the lower limit of the lowest class is 10. The upper limit of the highest class is

1. 15

2. 25

3. 35

4. 40

The class marks of a frequency distribution are given as follows :

15, 20, 25, ………

The class corresponding to the class mark 20 is

1. 12.5 - 17.5

2. 17.5 - 22.5

3. 18.5 - 21.5

4. 19.5 - 20.5

A grouped frequency distribution table with class intervals of equal size using 250 - 270 (270 not included in this interval) as one of the class intervals is constructed for the following data :

268, 220, 368, 258, 242, 310, 272, 342, 310, 290, 300, 320, 319, 304, 402, 318, 406, 292, 354, 278, 210, 240, 330, 316, 406, 215, 258, 236.

The frequency of class 310 - 330 is

1. 4

2. 5

3. 6

4. 7

The mean of x - 1, x + 1, x + 3 and x + 5 is

1. x + 1

2. x + 2

3. x + 3

4. x + 4