In the class intervals 10 - 20, 20 - 30, the number 20 is included in

1. 10 - 20

2. 20 - 30

3. both the intervals

4. none of these intervals

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 five numbers is 30. If one number is excluded, their mean becomes 28. The excluded number is

1. 28

2. 30

3. 35

4. 38

If the mean of x₁, x₂ is 7.5, and the mean of x₁, x₂, x₃ is 8, then the value of x₃ is

1. 9

2. 8

3. 7.5

4. 6