1. Calculate Class and their frequency table

X	Cumulative Frequency
20	15
30	40
40	60
50	72
60	80
70	85
80	88

Solution:
First we convert Cumulative frequency table to gropued frequency table

<	Cumulative Frequency
< 20	15
< 30	40
< 40	60
< 50	72
< 60	80
< 70	85
< 80	88

Class and their frequency table is

Class	Cumulative Frequency	Frequency
10 - 20	15	15 (= 15)
20 - 30	40	25 (= 40 - 15)
30 - 40	60	20 (= 60 - 40)
40 - 50	72	12 (= 72 - 60)
50 - 60	80	8 (= 80 - 72)
60 - 70	85	5 (= 85 - 80)
70 - 80	88	3 (= 88 - 85)

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2. Calculate Class and their frequency table

X	Cumulative Frequency
25	110
30	280
35	360
40	405
45	445
50	480

Solution:
First we convert Cumulative frequency table to gropued frequency table

<	Cumulative Frequency
< 25	110
< 30	280
< 35	360
< 40	405
< 45	445
< 50	480

Class and their frequency table is

Class	Cumulative Frequency	Frequency
20 - 25	110	110 (= 110)
25 - 30	280	170 (= 280 - 110)
30 - 35	360	80 (= 360 - 280)
35 - 40	405	45 (= 405 - 360)
40 - 45	445	40 (= 445 - 405)
45 - 50	480	35 (= 480 - 445)

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