A) 4:1 | B) 5:3 |

C) 16:1 | D) 1:16 |

Explanation:

Time taken by 8th tap = = 8 hours

and time taken by 12th tap = = hour

Ratio of time taken by 8th 8th tap and 12th tap = =16:1

Therefore, Ratio of efficiencies of 8th tap and 12th tap =1:16

A) 3 hrs | B) 6 hrs |

C) 7 hrs | D) 5 hrs |

Explanation:

Suppose A, B and C take x, x/2 and x/3 respectively to finish the work.

Then, (1/x + 2/x + 3/x) = 1/2

6/x = 1/2 => x = 12

So, B takes 6 hours to finish the work.

A) 51/24 | B) 87/5 |

C) 57/12 | D) 60/11 |

Explanation:

A can complete the work in 12 days working 8 hours a day

=> Number of hours A can complete the work = 12×8 = 96 hours

=> Work done by A in 1 hour = 1/96

B can complete the work in 8 days working 10 hours a day

=> Number of hours B can complete the work = 8×10 = 80 hours

=> Work done by B in 1 hour = 1/80

Work done by A and B in 1 hour = 1/96 + 1/80 = 11/480

=> A and B can complete the work in 480/11 hours

A and B works 8 hours a day

Hence total days to complete the work with A and B working together

= (480/11)/ (8) = 60/11 days

A) 120 days | B) 119 days |

C) 118 days | D) 117 days |

Explanation:

K's work in a day(1st day) = 1/30

L's work in a day(2nd day)= -1/60(demolishing)

hence in 2 days, combined work= 1/30 - 1/60

=1/60

since both works alternatively, K will work in odd days and L will work in even days.

1/60 unit work is done in 2 days

58/60 unit work will be done in 2 x 58 days = 116 days

Remaining work = 1-58/60

= 2/60

= 1/30

Next day, it will be K's turn and K will finish the remaining 1/30 work.

hence total days = 116 + 1 = 117.

A) 2 days | B) 3 days |

C) 4 days | D) 5 days |

Explanation:

work done=total number of person x number of days;

half of work done = 140 x 66;

For half of remaining work 25 extra men are added.

Therefore, total men for half work remaining = 140 + 25 = 165;

Let 2nd half work will be completed in K days;

140 x 66 = 165 x K

K = 122;

Hence, extra days => 122-120 = 2days.

A) 25 | B) 24 |

C) 23 | D) 21 |

Explanation:

(A+B+C) do 1 work in 10 days.

So (A+B+C)'s 1 day work=1/10 and as they work together for 4 days so workdone by them in 4 days=4/10=2/5

Remaining work=1-2/5=3/5

(B+C) take 10 more days to complete 3/5 work.

So( B+C)'s 1 day work=3/50

Now A'S 1 day work=(A+B+C)'s 1 day work-(B+C)'s 1 day work=1/10-3/50=1/25

A does 1/25 work in in 1 day

Therefore 1 work in 25 days.