Write your answer as a fraction

Question

James can paint the office​ by himself in 5 hours. Dave can do the same job in 8 hours. How long will it take them to do it working together?

Answer 1

This is a combined work problem. If James can paint the whole room in 5 hours, then he can do 1/5 of the job in an hour. Similarly, Dave can do 1/8 of the job in an hour. To find how fast they can complete the job working together, use the following equation:

1/5 + 1/8 = 1/t, where t = the total time James and Dave work on the project together

Solve this equation for t by finding the least common denominator of the two fractions on the left.