Assertion (A) : In the exclusive form, the upper and lower limits of a class are respectively known as the true upper limit and true lower limit.

Reason (R) : Class size = $\dfrac{\text{ True lower limit} + \text{ True upper limit}}{2}$

1. A is true, R is false

2. A is false, R is true

3. Both A and R are true

4. Both A and R are false

Age of teachers of a school varies from 24 years to 72 years. Rishabh has to make a grouped frequency distribution table of age of teachers. Which among the following class intervals of age will be most appropriate to make meaningful conclusion in less time and effort?

1. 24 - 26, 26 - 28, 28 - 30, and so on

2. 24 - 30, 30 - 36, 36 - 42, and so on

3. 24 - 48, 48 - 72

4. none of these

Range of 14, 12, 17, 18, 16 and p is 20. If p>0, then p= ?

1. 10

2. 26

3. 32

4. 35

The class mark of a class-interval is 'a'. If its lower limit is a-b, then its upper limit is :

1. a + b

2. ab

3. b-a

4. 2b