If the class intervals of a frequency distribution are `1-10, 11-20, 21-30, ….,51-60` then the size of even class is

Options

A. 9
B. 10
C. 11
D. 5.5

Answer

To find the size of the even class in the given frequency distribution with class intervals `1-10, 11-20, 21-30, ..., 51-60`, we will follow these steps:

### Step-by-Step Solution:

1. **Identify the Class Intervals**:
The class intervals provided are:
- 1 to 10
- 11 to 20
- 21 to 30
- 31 to 40
- 41 to 50
- 51 to 60

2. **Determine the Size of the Even Class**:
To find the size of the even class, we need to calculate the difference between the upper limit of the even class and the lower limit of the even class.

3. **Find the Lower Limit and Upper Limit of the Even Class**:
- The even class we are interested in is `21 to 30`.
- The lower limit of this class is `21`.
- The upper limit of this class is `30`.

4. **Calculate the Size of the Even Class**:
The size of the class is calculated as:
\[ \text{Size of the class} = \text{Upper Limit} - \text{Lower Limit} \]
Substituting the values:
\[ \text{Size of the class} = 30 - 21 = 9 \]

5. **Verify the Calculation**:
To ensure the calculation is correct, we can check the sizes of other classes:
- Size of `1-10` = 10 - 1 = 9
- Size of `11-20` = 20 - 11 = 9
- Size of `21-30` = 30 - 21 = 9
- Size of `31-40` = 40 - 31 = 9
- Size of `41-50` = 50 - 41 = 9
- Size of `51-60` = 60 - 51 = 9

All classes have the same size of 9.

### Conclusion:
The size of the even class (21 to 30) is **9**.