8 Jun 2017

7 - Perfect Shortcuts for Time and Work Problems - SBI Clerk / IBPS Exams 2017

7 - Perfect Shortcuts for Time and Work Problems - SBI Clerk / IBPS Exams 2017
7 - Perfect Shortcuts for Time and Work Problems - SBI Clerk / IBPS Exams 2017:
Dear Readers, Here we have given the 7 Perfect Shortcuts for Time and Work Problems for SBI Clerk / IBPS Exams 2017, candidates those who are preparing for the upcoming SBI Clerk/IBPS Exams 2017 can make use of it.


Type 1:
If number of persons engaged in doing a certain job is changed in the ratio of x:y, the days required in completion of work will change in the ratio of y:x
If m1 men can do a work in d1 days and m2 men can do the same work in d2 days, then man days  =(m1× d1 = m2×d2)
Example:
1) 12 men can do a work in 25 days. How long will 10 men take to complete the work?
a) 27 days    b) 28 days    c) 30days    d) 50 days
Solution:
Time taken by 10 men = (12 × 25) / 10 = 30 days

2) If a job is to complete in 10 days, it requires 270 persons. If 180 persons take up the same job, they will finish it in
a) 15 days  b)18 days    c) 27 days     d) 12 days
Solution:
(10 × 270) / 180 = 15 days

Type 2:
A and B working together can do a piece of work in x days whereas B working alone can do the same work in y days. How many days will A alone take to do the work?
(A+B)’s one day’s work = 1/x ;  B’s one day’s work = 1/y
A’s one day’s work = 1/x – 1/y = y-x/xy
--> A alone will complete the work in xy / y-x days.
Example:
1) A and B together can do a piece of work in 12 days, while B alone can finish it in 30 days. A alone can finish the work in:
a) 15 days    b) 20 days    c) 25 days    d) 18 days
Solution:
Time taken by A  = (30*12) / (30-12) = 20 days

Type 3:
If A is x times efficient than B, and working together they finish a work in y days. Then time taken by A = y(x+1) / x and time taken by B = y(x+1)
Example:
1) A and B can do a job together in 12 days. A is 2 times as efficient as B. in how many days can B alone complete the work
a) 18days     b) 12days     c) 36days     d) 9days
Solution:
Time taken by B = 12×(2+1) = 12×3 = 36 days

Type 4:
If A can do a piece of work in x days and B in y days. In how many days, both working together will finish the work?
A’s one day’s work = 1/x and B’s one day’s work = 1/y
A’s and B’s one day’s work = 1/x + 1/y = x+y/xy
Then A and B will do the work in xy/x+y days
Example:
1) If A can do a piece of work in 20 days and B in 30days. In how many days, both working together will finish the job?
a) 25      b)18    c) 12     d) None of this
Solution:
Time taken by A and B = 20×30/20+30 = 12days

Type 5:
If 'a' men or 'b' women can do a piece of work in x days.
Then 'm' men and 'n' women together can finish the work in abx/(an+bm)
Example:
1) 2 men or 4 women can do a work in 28 days. How long will 4 men and 8 women take to complete the work?
a) 7days     b) 14 days  c) 28 days     d) 56 days
Solution:
Time taken = (2 × 4 × 28)/ (2×8 + 4×4)
=(2×4×28)/32 = 7days

Type 6:
1) If 6 men dig 100 meters in 20 days working 8 hours  ,  how many men are required to dig 200 meters  in 10 days working 4 hours?
Solution:
The formula for solving such problem is
(M1 x D1 x H1)/W1=(M2 x D2 x H2)/W2
So the solution can be found out by the foresaid formula as under
6 x 20 x8/100 = M2 x 10×4/200
= 6×8 =48days

Type 7:
If A& B together can finish the work in x days,B& C together finishes in  y days and C& A together finishes in z days,then work done by A,B and C together in 1 day is
 

1) A and B together can complete a piece of work in 6 days. B and C can complete the same work in 8 days.A and C can finish it in 12 days. If they all work together, how long it will take to finish the work
 Solution:

Work done by A,B & C together in one day= ½(1/6 +1/8 + 1/12)=9/48
Then,Number of days taken to complete the work by A,B & C together =48/9 days


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