9. If the mean of the distribution is 57.6 and the sum of its observations is 50, find the missing

frequencies f1

and f2

C.I-

0-20 20-40 40-60 60-80 80-100 100-120

Fi

7 f1 12 f2 8 5

We have the following data

Class | Frequency
| Mid-values
| f ixi | |

0-20 | 7 | 10 | 70 | |

20-40 | f _{1} | 30 | 30f _{1} | |

40-60 | 12 | 50 | 600 | |

60-80 | f _{2} | 70 | 70f _{2} | |

80-100 | 8 | 90 | 720 | |

100-120 | 5 | 110 | 550 |

Since,

Again,

Multiply equation 1 by 3 and subtract it from equation 2 to get,

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