Friday, 15 April 2016

[Q] Time and Work Tricks - 3

Please read Part - 1 and Part - 2 before reading this post.


Here W  is the work. For e.g., if 5 men are cutting 10 trees in 2 days, working 4 hours per day. Then,
M = 5, D = 2, H = 4 and W = 10.

Q. 1)
H1 = 6
D1 = 18
D2 = 12
H2 = ?
We know, H1 * D1 = H2 * D2
6 * 18 = H2 * 12
H2 = 9 hours
Answer : (B)


Q. 2)

M1 = 15
D1 = 20
H1 = 8
M2 = 20
D2 = 12
H2 = ?
We know, M1 * D1 * H1 = M2 * D2 * H2
15*20*8 = 20*12*H2
H2 = 10 hours
Answer : (B)


Q. 3)

In this question, Taps = Men
Number of taps required = 20*9/15 = 12
Answer : (B)


Q. 4)

Let there be X number of men.
X men can finish a piece of work in 100 days. Hence total work = 100X
If there were (X - 10) men, it would have taken 110 days to finish the work. Total work in this case = 110(X - 10)
Total work remains the same. Hence,
100X = 110(X - 10)
X = 110
Answer : (D)


          Q. 5)

Efficiency of Subhash = 50/10 = 5 per hour
Efficiency of Subhash and Prakash = 300/40 = 7.5 per hour
Efficiency of Prakash = (Efficiency of Subhash and Prakash) - (Efficiency of Subhash) = 7.5 - 5 = 2.5
So Prakash can copy 2.5 pages per hour. To copy 30 pages, he would require 30/2.5 or 12 hours.
Answer : (D)


                                        Q. 6)

40 men can finish a work in 60 days. Hence, total work = 40*60 = 2400
Let the 10 men left after X days.
For X days, all the 40 men worked. Total work performed = 40X
Now when 10 men quit, only 30 men were left to do the work and they took (70 - X) more days to finish it.
Total work done by 30 men = 30*(70 - X)
Now, 40X + 30*(70 - X) = 2400
X = 30 days
Answer : (C)


Q. 7)

Let the total work = 360 units
Efficiency of A = 360/45 = 8 units
Efficiency of B = 360/40 = 9 units
Efficiency of A + B = 17 units
Let A left after X days.
For X days, both A and B worked. Hence work performed = 17X
B worked for 23 days. Hence work performed by B = 23*9 = 207 units
Now, 17X + 207 = 360
X = 9 days
Answer : (D)

Q. 8)

B and C together do 8/23 of the work, hence A does (1 - 8/23) or 15/23 of the work.
A should be paid = 15*5290/23 = Rs. 3450
Answer : (D)
Note : In this question, they have asked the wages of A. Had they asked the wages of B, firstly you would have calculated the work performed by B with the formula-
Work done by B = (Portion of work done by A and B) + (Portion of work done by B and C) - 1
Work done by B = 19/23 + 8/23 - 1 = 4/23
Wages of B = 4*5290/23 = Rs. 920

Q. 9)


This is a very famous question. A company employed 200 workers to complete a certain work in 150 days. Here the total work is not 200*150 because 200 workers and 150 days was only a plan. In reality, only 1/4th of the work has been done in 50 days. So if they go with the same pace, 200 workers will take 200 days to complete the work.
So total work = 200*200 units
200 workers have worked for 50 days. Hence they have finished 200*50 units of work.
Remaining work = 200*200 - 200*50 = 200*150
Let the number of additional workers required = X.
Now (200+X) workers will work for 100 days to finish the work as per the schedule.
Work they need to perform = (200 + X)*100
Now, (200 + X)*100 = 200*150
X = 100
Answer : (C)


Q. 10) A contractor undertook to finish a certain work in 124 days and employed 120 men.After 64 days,he found that he had already done 2/3 of work. How many men can be discharged now so that the work may finish in time?
A) 56             B) 44               C) 50               D) 60

120 workers finish 2/3 of the work in 64 days. So to complete the whole work, workers will take 64*3/2 or 96 days.
Total work to be performed = 120*96
Now the workers have already finished 2/3 of the work and only 1/3 work has to be performed.
Remaining work = 120*96/3 = 120*32
Let the contractor discharges X men. Remaining workers = 120-X. These workers will continue the work for (124-64) or 60 days. Hence,
120*32 = (120-X)*60
X = 56
Answer : (A)
Method 2
M1 = 120, D1 = 64, W1 = 2/3
M2 = 120 – x, D2 = 60, W2 = 1/3
(M1*D1)/W1 = (M2*D2)/W2
120*64*3/2 = (120 - x)*60*3
x = 56
Q. 11)

Let the second pipe fills the pool in X hours. Then first pipe takes (X+5) hours and the third pipe takes (X-4) hours to fill the pool. Now, 1st and 2nd pipe together take the same time to the fill the pool as the 3rd pipe alone. Hence,
1/(X+5) + 1/(X) = 1/(X - 4)
Solve this quadratic equation and you will get X = 10 hours
That means second pipe takes 10 hours to fill the pool while the third pipe takes 6 hours. Together they will take 10*6/(10 + 6) hours to fill the pool.
Answer: (B)


I have covered almost all the possible questions from Time and Work that are asked by SSC. If you have any doubt in this topic, please drop a comment.
Keep Reading :)

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42 comments:

  1. sir is type k ques ko short me btaiye

    Two alloys A and B contain gold and silver in the ratio of 1 : 2 and 1 : 3 respectively. A third alloy C is formed by mixing A and B in the ratio of 2 : 3. Find the percentage of silver in the alloy C

    ReplyDelete
    Replies
    1. Hello bhai apna con number dede mere se poora ratio ka chapter aata h with short trick meri Email id h
      sumitpal12595@gmail.com ispe bhej diye

      Delete
  2. sir in reasoning i face problem in solving 1.missing number
    2. a_b_ _ c_a_
    either it takes time to solve these two type problems or not able to solve at all. Plz tell the how to approach these type of questions . sometimes the missing letter series is too tough to make any pattern

    ReplyDelete
  3. A contractor undertook to finish a certain work in 124 days and employed 120 men.After 64 days,he found that he had already done 2/3 of work. How manu men can be discharged now so that the work may finish in time?

    Pls solve

    ReplyDelete
    Replies
    1. Q.9 ki tarah solve karo.
      2/3 work karne me 64 days lag rahe hain, that means pura work karne me 96 days lagenge.
      Total work = 120*96
      Rest is your home-work :P

      Delete
    2. it can also be done like the method you have explaine the first question..

      Delete
    3. This comment has been removed by the author.

      Delete
  4. Sir mere mock test me 110-115 bante hai....
    Resoning-40-43
    Quant -40-45
    Eng- 20-22
    G s -10-20
    Sir pls English k liye batao kuchh kyuki tier 2 me bhi English ka separate paper hoga 200 marks to main kaise English me score kr sakta hu????
    Please help me @parshant sir
    Its heartly humble request ....����

    ReplyDelete
    Replies
    1. Bro somehow manage Tier-1, I will post english articles once Tier-1 is over.
      In the mean time you can read "Sentence Correction" chapter from SP Bakshi and on a daily basis you should memorize 15 words, idioms, one-word substitution and phrasal verbs.

      Delete
    2. Yaah.. I have Paramount English module.
      Isn't it enough for tier 1??
      Otherwise thank you so much

      Delete
    3. I have just started cgl preparation 15 days ago , I've read only one third of Paramount book but confused in solving the questions ...therefore i couldn't score well in mock test....

      Delete
  5. Thank you so much sir...Like this plz try to Complete other tropics as soon as possible sir because exam is too close...it be so much useful for our preparation ..Thanks alot for your kindness sir..

    ReplyDelete
  6. This comment has been removed by the author.

    ReplyDelete
  7. sin@+sin^2@+sin^3@=1 then cos^6@-4cos^4@+8cos^2@ is equal to question was asked in 8.07.2012 cgl ...sir please give a solution of it..by assuming value of @ is not working here ...if any trick will work on this question so please share a trick sir

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  8. This comment has been removed by the author.

    ReplyDelete
  9. Sir seriously you covered each and every topic.....and your way of teaching is also lucent....you are doing social work....keep writing for us.....thankyu so much sir

    ReplyDelete
  10. sir according to newspaper report will ssc tier 1 qualifying and the exam will be onlineand the date will be postponded. sir is it true

    ReplyDelete
    Replies
    1. don`t go by hindi newspaper ...they don`t have credibility

      Delete
  11. a,b,c undertake to complete a piece of work for Rs 2574. A works for 8 days, b for 9 days and c for 12 days. If their daily wages are in the ratio of 3:4:5 what does c get?

    ReplyDelete
    Replies
    1. hey, i calculated the total work units which came out to be 72.
      therefore efficiency came out to be A=9, B=8, C=6.
      therefore the ratios should be 27:32:30.

      i did not get how wages will be in the ratio of 24:45:48.

      please explain. :(

      Delete
    2. No you cant calculate the efficiency because no where it is written that A "completes" the work in 8 days. A just works for 8 days.
      Let the wages of A, B and C be 3x, 4x and 5x
      A works for 8 days, hence total wages of A = 8*3x = 24x
      B works for 9 days, hence total wages of B = 9*4x = 36x
      C works for 12 days, hence total wages of C = 12*5x = 60x
      Ratio of wages of A, B and C = 24x:36x:60x = 2:3:5
      C gets = 5*2574/10 = Rs. 1287

      Sorry in the previous reply I had written a wrong ratio.

      Delete
    3. Okay thanks a lot. I guess my book has wrong answer for this question too. The answer was 1056. But I got the solution.

      Delete
  12. A can complete a job in 12 days, b in 15 days. Both of them worked for 5 days and rest of work was finished by c. If total earning is Rs 720. Find wages of b.

    ReplyDelete
    Replies
    1. total work = 60 units
      efficiency of B = 60/15 = 4
      work done by B in 5 days= 5*4 =20
      earning of B = 20/60 * 720

      Delete
    2. hey... got the correct answer...thanks :)

      Delete
  13. A b and c undertake to do a work For Rs 660 . A and b together do 5/8th of the work and remaining is done by c alone. How much should c get?

    ReplyDelete
    Replies
    1. work done by C = 3/8
      wage = 3/8*660

      Delete
    2. hey..really thanks for quick response but the answer is rs 180. a possibility answer is wrong?

      Delete
    3. Yes... the answer is wrong. Rs. 180 should be the answer to this question -
      A b and c undertake to do a work For Rs 660 . A and b together do 8/11 of the work and remaining is done by c alone. How much should c get?

      Delete
    4. okay. got it. thanks a ton!!

      Delete
  14. sIR Exam ab postpone ho gya aap english class start kr do plz

    ReplyDelete
  15. sir,kindly explain 6 th question,
    i am using MDH/W =constant(the same formula you have given above)

    men days work
    40 60 1 full unit
    40 x x/60 units completed
    30 (70-x) 59x/60 is remaining

    now
    (40* 60)/1 = (30(70-x))/(59x/60)

    on solving this am not getting answer,its in fractions 210/239.


    Kindly explain when i am doing wrong,please sir.

    ReplyDelete
  16. sir,kindly explain 6 th question,
    i am using MDH/W =constant(the same formula you have given above)

    men days work
    40 60 1 full unit
    40 x x/60 units completed
    30 (70-x) 59x/60 is remaining

    now
    (40* 60)/1 = (30(70-x))/(59x/60)

    on solving this am not getting answer,its in fractions 210/239.


    Kindly explain when i am doing wrong,please sir.

    ReplyDelete
  17. is there any other way to solve this ques? the calculation is time consuming.

    ReplyDelete
  18. Just use the formula M1*D1 = M2*D2
    40*60 = (40*x)+ (40-10)(70-x)
    x is no.of days after which 10 men left the work.

    ReplyDelete
  19. http://vintageitsolutions.com/best-computer-franchise-india

    ReplyDelete