Question

The marks of 80 students in Maths (out of 80) were recorded as follows:
Marks
0-20 21-30 40-60 61-80
Number of students 18 19 23 T 20
It the passing marks are 50% then find the probability that the student
chosen at random:
(1) got the passing marks
(11) failed to get the passing marks
(iii) got below 21 marks.
IX-MATHS
10​

Answer 1

Step-by-step explanation:

s,no    marks                   students

1          0-20                           18

2         21-30                          19

3         40-60                          23

4          61-80                         20

ans  1)   got passing marks > 50% which is above 40 marks = 23 + 20 =43

     2) got passing marks < 50% which is below  40 marks = 19 + 18 =37

3) got  marks <  21  marks = 18    

     

     

     

     

     

     

     

     

     

     

     

     

     

     

     

Answer 2

Given :

Marks     Number of students

0-20                 18

21-30                19

40-60               23

61-80                20

Passing marks is 50%

Total no. of students : 80

To find :

Find the probability that the student  chosen at random:

(1) got the passing marks

(11) failed to get the passing marks

(iii) got below 21 marks.

Solution :

Passing marks = 50%

Passing marks = 80 × 50 / 100

Passing marks = 40

1) Total students = 80

Students with passing marks = 23 + 20 = 43

Probability = 43 / 80

2) Students who failed to get the passing marks = 18 + 19 = 37

Probability = 37 / 80

3) Students who got below 21 marks = 18 / 80

Probability = 18 / 80 = 9 / 40