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Showing posts with label solving work and time problems formulas. Show all posts
Showing posts with label solving work and time problems formulas. Show all posts

Thursday 9 July 2015

Work and Time problems shortcuts for bank tests

Work and Time shortcut tricks for bank exams:In every competitive exam we have to deal with varieties of quantitative aptitude questions .In almost every competitive exam, work and time problem is a regular question under quantitative section.In bank PO and clerk exams there will be at least 2-3 questions on work and time.By understanding the basic concept and memorizing a few shortcut formulas, you  can score full mark for these questions.Here we are sharing some useful Work and Time shortcut tricks for bank exams.
Basic point to remember while solving work and time problems:First of all work done in 1 day is calculated.If a person completes a work in x days,then Work done by that person in one day is 1/x.
work and time problem shortcuts

Shortcut formula for solving work and time problems

If A can do a work in x days and B can do the same work in y days,then  A and B together can finish the work in 
work and time formula
This is the first and foremost shortcut formula for solving work and time problems.For understanding better, derivation of this formula is given below.
Derivation of above formula:
    Work done by A in one day=1/x
    Work done by B in one day=1/y
    Work done by A and B together in 1 day=1/x+1/y
    Then  total days taken to complete the work by A and B together=1/ Work done by A and      B together in 1 day
    =1/(1/x+1/y)
    =1/((x+y)/xy))
    =xy/(x+y)

Example:If A can do a work in 8 days and B can do the same work in  days,in how many days A and B together can finish the work
Ans:Applying above formula 
 no of days taken to finish the work=8*6/(8+6)
 Instead of solving this directly take the LCM of 8 and 6
 8*6/(8+6)=LCM(8,6)/(LCM(8,6)/8 + LCM(8,6)/6)=24/(3+4)=24/7=3 3/7

Important points to be noted while solving work and time problems

  1. If A completes a work in x days and B completes the same work in y days then ratio of work done by A and B in one day will be y:x
  2. If A can finish the work in x days ,B can finish the same work  in y days and C finishes it in z days, then number of days taken to complete the work if all three work together is  work and time shortcut trick formula 
  3. 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                            work and time shortcut trick formula
  4. If a man can do x/y of work in 1 hr,then he will take y/x hrs to finish the work.

Work and Time - Practice questions(Solved)

Question1:Ganesh ,Ram and Sohan together can do a work in 16 days. If Ganesh and Ram together can do a the same work in 24 days then, how long will take Sohan to do the same work?
Solution: Work done by three of them together in 1 day= 1/16............(1)
               Work done by Ganesh and Ram together in 1 day= 1/24.....(2)
               So,work done by Sohan in one day=(1)- (2)=(1/16) - (1/24)=1/48
               =>Total days taken by Sohan to complete the work alone= 48 days.

Question2:15 men can complete a work in 10 days while 20 boys can complete the same work in 15 days .How many days will 10 men and 10 boys together take to complete the same work
Solution:Work done by one man in one day=1/(15*10)
              Work done by one boy in one day=1/(20*15)
              Work done by 10 men and 10 boys in one day=10[ 1/(15*10) + 1/(20*15)] 
              Days taken=1/Work done by 10 men and 10 boys in one day
                                =10 days

Question3:16 men can do a piece of work in 16 days .4 days after they started the work, 8 more men joined them. How many days will they now take to complete the remaining work
Solution:Work done by 1 man in 1 day=1/(16*16)
              Work completed by 16 men in 4 days= 4[1/(16*16)]*16=1/4
               Remaining work= 1- 1/4= 3/4
               Total men now= 16+ 8=24
               24 men do 3/4 work 
                =>24*number of days*Work done by 1 man in 1 day=3/4
                =>24*number of days* 1/(16*16)=3/4
                =>number of days=8 days

Download Work and Time Practice questions PDF ebook
Question4: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:Applying the formula
               Work done by A,B & C together in one day= ½(1/6 +1/8 + 1/12)=9/48
                => days taken to complete the work by A,B & C together =48/9 days


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