Question

Find the number of students who obtained less than 45 marks from the following data.
Marks
30-40
40-50
50-60
60-70
70-80
Numberof students
31
42
51
35
31

Answer 1

Convert the continuous class interval

$\frac{lower \: limit + upper \: limit}{2}$

30+40/2 = 70/2= 35

40+50/2 = 90/2 = 45

50+60/2 = 110/2 = 55

60+70/2 = 130/2 = 65

70+80/2 = 150/2 = 75

The class interval are (Marks)

35 - 31

45 - 42

55 - 51

65 - 35

75 - 31

so the no of students who obtained less than 45

is 31 students