# NCERT Mathematics Class 9 Exemplar Ch 14 Statistics and Probability Part 15 (For CBSE, ICSE, IAS, NET, NRA 2022)

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Q. 10. The mean of the following distribution is 50.

x | f |

10 | 17 |

30 | |

50 | 32 |

70 | |

90 | 19 |

Find the value of a and hence the frequencies of 30 and 70.

Answer: , frequency of 30 is 28 and that of 70 is 24.

Q. 11. The mean marks (out of 100) of boys and girls in an examination are 70 and 73, respectively. If the mean marks of all the students in that examination are 71, find the ratio of the number of boys to the number of girls.

Answer:

Q. 12. A total of 25 patients admitted to a hospital are tested for levels of blood sugar, (mg/dl) and the results obtained were as follows:

87 | 71 | 83 | 67 | 85 |

77 | 69 | 76 | 65 | 85 |

85 | 54 | 70 | 68 | 80 |

73 | 78 | 68 | 85 | 73 |

81 | 78 | 81 | 77 | 75 |

Find mean, median and mode (mg/dl) of the above data.

Answer: Mean , Median , Mode