Maths by Mr. M. P. Keshari

**Example 4. **Out of 400 bulbs in a box, 15 bulbs a defective. One ball is taken out at random from the box. Find the probability that the drawn bulb is not defective.

**Solution:-** Total number of bulbs = 400

Total number of defective bulb = 15

Total number of non-defective bulbs = 400-15

= 385

P (not defective bulb) = 385/400

= 77/80

**Example 5. **Find the probability of getting 53 Fridays in a leap year.

**Solution:-** No. of days in a leap year = 366

366 days = 52 weeks and 2 days.

A leap year must has 52 Fridays

The remaining two days can be

- Sunday an Monday
- Monday and Tuesday
- Tuesday and Wednesday
- Wednesday and Thursday
- Thursday and Friday
- Friday and Saturday
- Saturday and Sunday

Out of 7 case, 2 cases have Friday

P (53 Friday) = 2/7

Maths by Mr. M. P. Keshari

Subjects |
Maths (Part-1) by Mr. M. P. Keshari |

Chapter 9 |
Circle |

Chapter 10 |
Tangents to a circle |

Chapter 11 |
Geometrical Construction |

Chapter 12 |
Troigonometry |

Chapter 13 |
Height and Distance |

Chapter 14 |
Mensuration |

Chapter 15 |
Statistics |

Chapter 16 |
Probability |

Chapter 17 |
Co-ordinate Geometry |