The Quick Way Through GMAT Work Problems
A category of question that appears regularly on the GMAT is that of work problems. A typical question involves one machine working at a particular rate, and another machine working at a different rate. The question may ask you to work out how long a job will take if both machines work on it together.
Here’s a popular strategy that you can use (stay tuned for our tutors’ favorite strategy next week):
1. Stick with this formula for simpler problems:
is the completion time for one machine, is the completion time for the other, and is the completion time when both machines work together. For example: Machine takes 6 hours to do a job. Machine takes 18 hours to do the same job. How long would it take to do the job if both machines worked together?
2. Applying the formula:
3. When things get trickier!
Take an example from Economist GMAT Tutor’s bank of questions:
Working alone, Manuel finishes cleaning half the house in a third of the time it takes Nick to clean the entire house alone. Manuel alone cleans the entire house in 6 hours. How many hours will it take Nick and Manuel to clean the entire house if they work together?
Solution: First, work out how long Nick takes to clean the house alone, using the various pieces of information given:
- Manuel cleans the entire house in 6 hours.
- Therefore, he cleans half the house in hours.
- This is one-third of the time it takes Nick to clean the whole house.
- Therefore, Nick takes hours to clean the house.
Second, apply the formula. We need the time they take together to clean one house (notice that ‘the house’ means one house):
These problems may sound complicated, but as long as you use the one formula required, you can solve them within the two-minute target time for each question.
This post appeared first on the Economist GMAT Tutor blog.