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Time and work problems are really important for many big exams, like those for bank jobs, government work, and railways. If you’re good at these, you have a better chance of doing well in these tests. To get good at time and work problems, you need to know some special formulas and clever tricks. These can help you solve questions faster and more easily. The time and work questions are the foundation of various other concepts including Data interpretation, and Data sufficiency. Read the article below to find the list of formulas tricks and questions that will help you clear your doubts about the subject matter.
Time & Work: Importance
Time And Work: Formulas
When you know the Time and Work formula, you can completely link that formula to the solution as soon as you read the question. Knowing Time & Work tricks will also help you solve the questions in a few seconds thus saving you time for other sections. You can find Time & Work formulas along with important Time & Work Tricks below.
1. Basic Formula:
Work = Rate × Time
Time = Work / Rate
Rate = Work / Time
2. Reciprocal of Rate: Sometimes, it’s easier to work with the reciprocal of the rate, which represents the work done per unit time.
Reciprocal of Rate = 1 / Rate
3. Combined Work:
If A can complete a task in ‘x’ days, then A’s work rate is 1/x.
If B can complete a task in ‘y’ days, then B’s work rate is 1/y.
When A and B work together, their combined work rate is 1/x + 1/y.
4: Time Taken by A and B Together:
If A and B work together, the time taken to complete the task is:
Time = 1 / (1/x + 1/y)
5. Time Taken by More than Two Workers:
When more than two workers are involved, the formula becomes:
Time = 1 / (1/x + 1/y + 1/z + …)
Time And Work: Questions And Tricks
- If A, B & C will work alone and can complete a work in x, y, and z days, respectively, then they will together complete the work in
- Two persons A & B, working together, can complete a piece of work in x days. If A, working alone can complete the work in y days, then B, working alone, will complete the work in
- If A & B working together can finish a piece of work in x days, B & C in y days, and C & A in z days. Then, A + B + C working together will finish the job is
- If A can finish a work in x days and B is k times more efficient than A, then the time taken by both A and B, working together to complete the work is
- If A & B working together can finish a work in x days & B is k times more efficient than A, then the time taken by,
- If A working Alone takes a day more than A & B, & B working Alone takes b-days more than A & B. Then,
a. 10 days
b. 15 days
c. 20 days
d. 25 days
Correct answer:(c)
Sol: Assume 1 man’s 1 day work = x & 1 boy’s 1 day work = y
From the given data, we can generate the equations as : 4x + 5y = 1/20 —(1) & 5x + 4y = 1/16 —(2)
By solving the simultaneous equations (1) & (2),
x = 1/ 80 & y = 0
Therefore, (4 men + 3 boys ) 1 day work = 4 x 1 + 3 x 0 = 1
80 20
Thus, 4 men and 3 boys can finish the work in 20 days.
Q. Sonal and Preeti started working on a project and they can complete the project in 30 days. Sonal worked for 16 days and Preeti completed the remaining work in 44 days. How many days would Preeti have taken to complete the entire project all by herself?
- 20 days
- 25 days
- 55 days
- 46 days
- 60 days
Correct answer: 60 days
Sol: Let the work done by Sonal in 1 day be x
Let the work done by Preeti in 1 day be y
Then, x+y = 1/30 ——— (1)
⇒ 16x + 44y = 1 ——— (2)
Solving equations (1) and (2),
x = 1/60
y = 1/60
Thus, Preeti can complete the entire work in 60 days
Q. P can complete a work in 12 days working 8 hours a day. Q can complete the same work in 8 days working 10 hours a day. If both p and Q work together, working 8 hours a day, in how many days can they complete the work?
Sol: P can complete the work in (12 x 8) hrs = 96 hrs
Q can complete the work in (8 x 10) hrs=80 hrs
Therefore, P’s 1 hour work=1/96 and Q’s 1-hour work= 1/80
(P+Q)’s 1 hour’s work =(1/96) + (1/80) = 11/480. So both P and Q will finish the work in 480/11 hrs
Therefore, Number of days of 8 hours each = (480/11) x (1/8) = 60/11
Q. (x-2) men can do a piece of work in x days and (x+7) men can do 75% of the same work in (x-10)days. Then in how many days can (x+10) men finish the work?
Sol: 34×(x−2)x=(x+7)(x−10)34×(x-2)x=(x+7)(x-10)
⇒x2−6x−280=0⇒x2-6x-280 =0
=> x= 20 and x=-14
so, the acceptable value is x=20
Therefore, Total work =(x-2)x = 18 x 20 =360 unit
Now 360 = 30 x k
=> k=12 days
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