Important for :

1

A

Amitabh can do a piece of work in 25 days.In 5 days he can do 1/5th work.

Rest work = 1 – | 1 | = | 4 |

5 | 5 |

Bindu can complete 4/5th of the work in 20 days so he can do the complete work in 25 days.

Amitabh's 1 day work = | 1 |

25 |

Bindu's 1 day work = | 1 |

25 |

(Amitabh and Bindu)'s 1 day work = | 1 | + | 1 | = | 2 |

25 | 25 | 25 |

Amitabh and Bindu together can complete the work in = | 25 | days |

2 |

Hence, option A is correct.

2

C

Let's Chandu can do the work in 2x days.Bhanu can do it in 6x days and Arnab can do it in 3x days.

1 | + | 1 | + | 1 | = | 1 | ⇒ | 3 + 1 + 2 | = | 1 | ⇒ x = 30 |

2x | 6x | 3x | 30 | 6x | 30 |

So, the time taken to complete the work by Arnab, Bhanu and Chandu is 90, 180, 60 days respectively.

Hence, option C is correct.

3

B

Combined work done by Vijay and Vinod in 4 + 6 days (4 initial days and last 6 days)= | 10 | + | 10 | = | 2 | |

24 | 40 | 3 |

∴ Remaining work = 1 – |
2 | = | 1 |

3 | 3 |

Rakesh works for | ( | 1 | × 30 | ) | = | 10 days |

3 |

Hence, option B is correct.

4

C

Given, Work done by (3 M + 2 W) = Work done by (2 M + 3 W)

⇒ 3 M – 2 M = 3 W – 2 W

⇒ 1 M = 1 W

⇒ M : W = 1 : 1

Option C is hence the correct answer.

5

D

Let the total work be 100%A can do the work in 5 days, so he can do 20% work in 1 day

B can do the work in 4 days, so he can do 25% work in 1 day

Together they can do 20+25 = 45% work in 1 day

Now the work is increased by 800%, so the work becomes 900%

The work can be done in | 900 | = 20 days |

45 |

Hence, option D is correct.