CAT Quantitative Aptitude Questions | CAT Time and Work questions

CAT Questions | Time and work | Work Time

The question is from Time and work. It is about two people working on alternative days to complete a task. Point to ponder: If they work together, will the number of days taken decrease?

Question 13: A can complete a task in 12 days. B can complete the task in 18 days. If A and B work on this same task in alternate days starting with A, in how many days do they finish the entire task?

  1. 10.8 days
  2. 14.33 days
  3. 11 days
  4. 8.4 days

Rs. 2500 off on 2IIM Ultimate DI LR Course for CAT 2019. Offer valid till March 24th.


Signup to sample the Best CAT Online Coaching


Best CAT Coaching in Chennai


Starts Sat, Mar 23, 2019


Explanatory Answer

Method of solving this CAT Question from Pipes Cisterns and Work Time: If they work together, will the number of days taken decrease?

A can complete a task in 12 days and B can complete the task in 18 days. So,
In one day, A can do \\frac{1}{12}\\), in one day B can do \\frac{1}{18}\\).
In two days, they can complete \\frac{1}{12}\\) + \\frac{1}{18}\\) = which is \\frac{5}{36}\\).
In 4 days, they can finish \\frac{10}{36}\\), and so on.
We can have 7 such sets of 2days each.
So, at the end of 14 days, they would have done \\frac{35}{36}\\) of task.
On the 15th day A would begin work with \\frac{1}{36}\\)of the task to finish. He can finish \\frac{1}{12}\\) in a day. So, he would take one-third of a day. So, they can finish the whole task in 14.33 days.

The question is "how many days do they finish the entire task?"

Hence, the answer is "14.33 days".

Choice B is the correct answer.

Online CAT Coaching
Try it free!

Register in 2 easy steps and start learning in 30 seconds!

★ Sign up for Free

Already have an Account?

★ Login to Continue

CAT Coaching in Chennai

Next Weekend Batch Starts Sat, Mar 23rd, 2019

★ CAT Coaching Info

Best CAT Coaching in Chennai

Sign up for a Free Demo of our CAT Coaching in Chennai

★ Schedule Demo


CAT Online Coaching | CAT Arithmetic Videos On YouTube


Other useful sources for Arithmetic Questions | Pipes Cisterns; Time and Work Sample Questions


CAT Questions | CAT Quantitative Aptitude

CAT Questions | CAT DILR

CAT Questions | Verbal Ability for CAT


Where is 2IIM located?

2IIM Online CAT Coaching
A Fermat Education Initiative,
10-C, Kalinga Colony, Bobbili Raja Salai
K.K.Nagar, Chennai. India. Pin - 600 078

How to reach 2IIM?

Phone: (91) 44 4505 8484
Mobile: (91) 99626 48484
WhatsApp: WhatsApp Now
Email: prep@2iim.com