Time and work questions are fastest when the job is a whole number of units rather than 1. Take the LCM of the given days, give each worker a rate in units per day, and the fractions disappear. Every walkthrough below does exactly that, which is why none of them contains a common denominator.
Download the PDF — 15 questions with answers
Free, ungated, no email. This is the time and work questions with answers PDF — the same 15 questions as below, with every worked solution at the back, ready to print.
The 15 questions below are ordered the way an exam block is rather than easiest-first: two gentle openers, then a run of medium, and a hard one every sixth question — 2 of the 15 sit in the hard band. Every question is a time & work.
Work each question on paper before you open its solution. The walkthrough is the method itself, step for step, so reading it first turns a practice set into a reading exercise and teaches nothing. If you are stuck on the method rather than on one question, the method guide is a better place to start than the next question: Time and work: the LCM unit method.
Every question below was generated by the same engine that mints the ComputePrep daily timed drill, and machine-checked before it reached this page — a multiple-choice question validates its own answer against its own options at generation, and ships only with a walkthrough attached. The walkthrough is the engine's own.
In how many hours will the tank be full?
An inlet pipe fills a tank in 20 hours; an outlet pipe empties the full tank in 30 hours.
Both pipes are opened together on an empty tank.
In how many hours will the tank be full?
An inlet pipe fills a tank in 20 hours; an outlet pipe empties the full tank in 30 hours.
Both pipes are opened together on an empty tank.
In how many hours will the tank be full?
An inlet pipe fills a tank in 15 hours; an outlet pipe empties the full tank in 30 hours.
Both pipes are opened together on an empty tank.
Working together, in how many days will Deepak and Latha finish it?
Deepak is 2 times as efficient as Latha.
Latha alone can finish the work in 12 days.
Working together, in how many days will they finish it?
Karan can complete a piece of work in 30 days.
Meera can complete the same work in 20 days.
In how many days will Shalini finish the remaining work?
Imran can finish a job in 6 days and Shalini can finish it in 12 days.
Imran works alone for 2 days, then leaves.
In how many hours will the tank be full?
An inlet pipe fills a tank in 20 hours; an outlet pipe empties the full tank in 30 hours.
Both pipes are opened together on an empty tank.
Working together, in how many days will they finish it?
Imran can complete a piece of work in 9 days.
Shalini can complete the same work in 18 days.
In how many hours will the tank be full?
An inlet pipe fills a tank in 16 hours; an outlet pipe empties the full tank in 48 hours.
Both pipes are opened together on an empty tank.
Working together, in how many days will they finish it?
Ravi can complete a piece of work in 30 days.
Sunita can complete the same work in 20 days.
Working together, in how many days will they finish it?
Karan can complete a piece of work in 16 days.
Meera can complete the same work in 48 days.
Working together, in how many days will they finish it?
Ravi can complete a piece of work in 24 days.
Sunita can complete the same work in 8 days.
Working together, in how many days will they finish it?
Deepak can complete a piece of work in 15 days.
Latha can complete the same work in 30 days.
In how many hours will the tank be full?
An inlet pipe fills a tank in 20 hours; an outlet pipe empties the full tank in 30 hours.
Both pipes are opened together on an empty tank.
Working together, in how many days will Anil and Bhavna finish it?
Anil is 3 times as efficient as Bhavna.
Bhavna alone can finish the work in 24 days.
Most free practice for this topic is a scanned upload or a blog quiz, and neither can tell you a question has exactly one answer. That is the one thing this set can promise: it is minted, not typed. The engine behind it serves ComputePrep's daily timed drill, so the questions here are the same shape as the ones a live round would give you — and there is an unlimited supply of them, which is why this page can be regenerated rather than padded.
If you want the method rather than more questions, Time and work: the LCM unit method covers the approach, the traps and a worked table. This page and that one deliberately answer different questions: that one is how do I solve these, this one is give me time and work questions with the answers.
Because it removes every fraction from the problem. If A takes 12 days and B takes 18, set the job at 36 units: A does 3 a day, B does 2, together 5. The answer is 36/5 days, reached without ever adding 1/12 and 1/18 — and without the arithmetic slip that usually causes.
Efficiency and time are inversely proportional. If A is twice as efficient as B, A takes half as long. Convert an efficiency ratio into a time ratio before doing anything else; carrying an efficiency ratio into a time formula is the standard way this family goes wrong.
Identical, with one addition: an outlet pipe has a negative rate. Set the tank at the LCM of the fill times, add the inlet rates, subtract the outlet rates, and divide. If the net rate is negative the tank never fills, and that is sometimes the intended answer.
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