*NCERT Solutions of Chapter: Probability. NCERT Solutions along with worksheets and notes for Class 9.*

**Exercise 15.1**

**(1)** **In a cricket match, a batswoman hits a boundary 6 times out of 30 balls she plays. Find the probability that she did not hit a boundary.**

**Ans-**

**(2)** **1500 families with 2 children were selected randomly, and the following data were recorded:**

Number of girls in a family |
2 |
1 |
0 |

Number of families |
475 |
814 |
211 |

**Compute the probability of a family, chosen at random, having**

**(i) 2 girls (ii) 1 girl (iii) No girl**

**Ans-**

**(3)** **Refer to Example 5, section 14.4, chapter 14. Find the probability that a student of the class was born in August.**

**Example 5**

**Ina particular section of class IX, 40 students were asked about the months of their birth and the following graph was prepared for the data so obtained:**

**Ans-**

**(4)** **Three coins are tossed simultaneously 200 times with the following frequencies of different outcomes:**

Outcome |
3 heads |
2 heads |
1 heads |
No head |

Frequency |
23 |
72 |
77 |
28 |

**If the three coins are simultaneously tossed again, compute the probability of 2 heads coming up.**

**Ans-**

**Ans-**

**(6)** **Refer to table 14.7, Chapter 14.**

**(i) Find the probability that a student obtained less than 20% in the mathematics test.**

**(ii) Find the probability that a student obtained marks 60 or above.**

**Table 14. 7, Chapter 14**

Marks |
Number of Students |

0 – 20 |
7 |

20 – 30 |
10 |

30 – 40 |
10 |

40 – 50 |
20 |

50 – 60 |
20 |

60 – 70 |
15 |

70 – above |
8 |

Total 90 |

**Ans-**

**(7)** **To know the option of the students about the subject statistics, a survey of 200 students was conducted. The data is recorded in the following table.**

Opinion |
Number of students |

Like |
135 |

Dislike |
65 |

**Find the probability that a student chosen at random**

**(i) likes statistics,**

**(ii) does not like it.**

**Ans-**

**Ans-**

**(9)** **Activity: Note the frequency of two – wheelers, three – wheelers and four wheelers going past during a time interval, in front of your school gate. Find the probability that any one vehicle out of the total vehicles you have observed is two – wheeler.**

**Ans-**

**(10)** **Activity: Ask all the students in your class to write a 3 – digit number. Choose any student from the room at random. What is the probability that the number written by her/him is divisible by 3? Remember that a number is divisible by 3, if the sum of its digits is divisible by 3?**

**Ans-**

**(11)Eleven bags of wheat flour, each marked 5 kg, actually contained the following weights of flour (in kg):**

**4.97 5.05 5.08 5.03 5.00 5.06 5.08 4.98 5.04 5.07 5.00**

**Find the probability that any of these bags chosen at random contains more than 5 kg of flour.**

**Ans-**

**(12) In Q.5 Exercise 14.2, you were asked to prepare a frequency distribution table, regarding the concentration of sulphur dioxide in the air in parts per million of a certain city for 30 days. Using this table, find the probability of the concentration of sulphur dioxide in the interval 0.12 – 0.16 on any of these days.**

**Q 5, Exercise 14.2**

**A study was conducted to find out the concentration of sulphur dioxide in the air in parts per million (ppm) of a certain city. The data obtained for 30 days is as follows:**

**0.03 0.08 0.08 0.09 0.04 0.17**

**0.16 0.05 0.02 0.06 0.18 0.20**

**0.11 0.08 0.12 0.13 0.22 0.07**

**0.08 0.01 0.10 0.06 0.09 0.18**

**0.11 0.07 0.05 0.07 0.01 0.04**

**Ans-**

The frequency distribution table of Q5, exercise 14.2 is given below-

Concentration of sulphur dioxide (in ppm) |
Frequency |

0.00 – 0.04 | 4 |

0.04 – 0.08 | 9 |

0.08 – 0.12 | 9 |

0.12 – 0.16 | 2 |

0.16 – 0.20 | 4 |

0.20 – 0.24 | 2 |

**Ans-**

**Helping Topics**