Question

The following grouped frequency distribution shows the time taken for students to solve a puzzle. 

Time is taken (seconds)	Frequency
0 < t ≤ 5	2
5 < t ≤ 10	9
10 < t ≤ 15	9
15 < t ≤ 20	8
20 < t ≤ 25	3
25 < t ≤ 30	1

The time by which 28 students had solved the puzzle will be:

1. 20
2. 15
3. 25
4. 10

Answer 1

Correct Answer - Option 1 : 20

Concept:

Cumulative frequency: Cumulative frequency distribution is the sum of the frequency of class and all classes below it in a frequency distribution.

This means we can get cumulative frequency by adding up a value and all of the values that came before it.

Calculation:

Time is taken (seconds)	Frequency	Cumulative frequency
0 < t ≤ 5	2	2
5 < t ≤ 10	9	11
10 < t ≤ 15	9	20
15 < t ≤ 20	8	28
20 < t ≤ 25	3	31
25 < t ≤ 30	1	32

 

Clearly, we can see that,

Time by which 28 students had solved the puzzle = 20.