**3. The marks scored by students in mathematics in a certain examination are given below:**

Marks scored |
1 – 20 |
21 – 40 |
41 – 60 |
61 – 80 |
81 – 100 |

Number of
students |
3 |
8 |
19 |
18 |
6 |

**Solution:**

**Let us make the continuous class interval.**

Marks scored |
Extended
Class |
Number of
students. |

1 – 20 |
0.5 – 20.5 |
3 |

21 – 40 |
20.5 – 40.5 |
8 |

41 – 60 |
40.5 – 60.5 |
19 |

61 – 80 |
60.5 – 80.5 |
18 |

81 – 100 |
80.5 – 100.5 |
6 |