IT takes Holly 5 hours to type a paper. It takes Mike 6 hours to type the same paper. HOw long would it take them working together? Just average?

1 answer

clearly not just the average, since that would be 5.5, or slower than Holly by herself.

You have to consider how much works gets done in 1 hour by each person. Then you can add that up to see how much gets done together.

1/5 + 1/6 = 11/30

so, the paper takes 30/11 hours for them together. Or, just under 3 hours.

Makes sense, since two Hollys could do it in 2.5 hours, and two Mikes would take 3 hours.