**Important Questions & Solutions of Class 9 Maths Chapter 14 – Statistics**

**ncert for class 9th maths**

**Question 1**. **Give three examples of data which you can get from your day-to-day life.**

**Solution:**

Here are the three examples which are related to our day-to-day life :

- The number of boys in a sports team.
- Electricity bills for last one year.
- The number of students appearing for board exams at your school.

**Question 2**. **The height of 20 students of class V are noted as follows**

**4, 4.5, 5, 5.5, 4, 4, 4.5, 5, 5.5, 4, 3.5, 3.5, 4.2, 4.6, 4.2, 4.7, 5.5, 5.3, 5, 5.5.**

**Make a frequency distribution table for the above data.****Which is the most common height and which is the rarest height among these students?**

**Solution:**

1. The required frequency distribution table is:

Height | Tally Marks | Students |

3.5 | II | 2 |

4 | IIII | 4 |

4.2 | II | 2 |

4.5 | II | 2 |

4.6 | I | 1 |

4.7 | I | 1 |

5 | III | 3 |

5.3 | I | 1 |

5.5 | IIII | 4 |

Total | 20 |

2. The most common heights are 4 and 5.5.

The rarest heights are 4.6 and 4.7.

**Question 3: The number of family members in 10 flats of society are**

**2, 4, 3, 3, 1,0,2,4,1,5.**

**Find the mean number of family members per flat.**

**Solution**:

Number of family members in 10 flats -2, 4, 3, 3, 1, 0, 2, 4, 1, 5.

So, we get,

Mean = sum of observation/ total no of observations

Mean = (2 + 4+ 3 + 3 + 1 + 0 + 2 + 4 + 1 + 5) / 10

Mean = 25/10 = 2.5

**Question 4.The following is the list of number of coupons issued in a school canteen during a week:**

**105, 216, 322, 167, 273, 405 and 346.**

**Find the average no. of coupons issued per day.**

**Solution:**

Number of coupons issued in a week: 105, 216, 322, 167, 273, 405 and 346.

So, we get,

Mean = sum of observation/ total no of observations

Mean = 106+ 215+ 323+166+273+405+346/ 7 = 1834/7

Mean = 262

**Question 5. The daily minimum questions solved by a student during a week were as under:**

Monday |
Tuesday |
Wednesday |
Thursday |
Friday |
Saturday |

35 |
30 |
27 |
32 |
23 |
28 |

**Find the mean.**

**Solution: **

Number of questions solved in a week: 35, 30, 27, 32, 23, 28.

So, we get,

Mean = sum of observation/ total no of observations = (35+30+27+32+23+28) / 7 = 175/7 = 25

**Question 6.If the mean of six observations y, y + 1, y + 4, y + 6, y + 8, y + 5 is 13, find the value of y.**

**Solution:**

Mean = sum of observation/ total no of observations

13 = (*y + y *+ 1+ *y* + 4+* y* + 6+ *y* + 8+ y + 5) / 6

13 = (6y + 24)/6

(13 * 6) = 6y +24

(13 * 6) – 24 = 6y

(13 * 6) – 6 * 4 = 6y

6(13 – 4) = 6y

y = 9

**Question 7.** **The mean weight of a class of 34 students is 46.5 kg. If the weight of the new boy is included, the mean is rises by 500 g. Find the weight of the new boy.**

**Solution:**

The mean weight of 34 students = 46.5

Sum of the weight of 34 students = (46.5 * 34) = 1581

Change or increase in the mean weight when the weight of a new boy is added = 0.5

So, the new mean = (46.5 +0.5) = 47

So, let the weight of the new boy be y.

So, (sum of weight of 34 students + weight of new boy) / 35 = 47

(1581+ y)/ 35 = 47

1581 + y = 1645

y = 1645 – 1581 = 64

**Question 8.The Number of books issued to 13 students in a class are:**

**25, 19, 24, 23, 29, 31, 19, 20, 22, 26, 17, 35, 21.**

**Find the median no. of books for the above data.**

**Solution:**

Let’s arrange the data given in ascending order – 17, 19, 19, 20, 21, 22, 23, 24, 25, 26, 29,31,35.

n= 13, so it’s an odd number

Median = (n+1) / 2 observations

= (13+1)/ 2 = (14/2)^{th} observation = 7th observation = 23

**Question 9.The weight (in kg) of 7 students of a class are 44, 52, 55, 60, 50, 49, 45.**

**Find the median weight.**

**Solution:**

Let’s arrange the data given in ascending order – 44, 45, 49, 50, 52, 55, 60.

n= 7, so it’s an odd number

Median = (n+1) / 2 observations

= (7+1)/ 2 = (8/2)^{th} observation = 4th observation = 50 kg

### Extra Questions For Class 9 Maths Chapter 14 (Statistics)

- Find the mean and median of the following data: 25, 26, 27, 28, 28, 29, 25, 30, 29
- The blood groups of 30 students of Class VIII are recorded as follows: A, B, O, O, AB, O, A, O, B, A, O, B, A, O, O, A, AB, O, A, A, O, O, AB, B, A, O, B, A, B, O. Represent this data in the form of a frequency distribution table. Which is the most common, and which is the rarest, blood group among these students?
- The value of π up to 50 decimal places is given below:

3.14159265358979323846264338327950288419716939937510

(i) Make a frequency distribution of the digits from 0 to 9 after the decimal point.

(ii) What are the most and the least frequently occurring digits?