Sue, an experienced shipping clerk, can fill a certain order in 9 hours. Felipe, a new clerk, needs 11 hours to do the same job. Working together, how long will it take them to fill the order?

Question

7151 views around the world

You can reuse this answer
Creative Commons License

Answer 1 · 2017-01-09T07:16:51

#4# hours and #57# minutes.

Here's one method:

The least common multiple of #9# and #11# is #99#.

In #99# hours, Sue could fill #99/9 = 11# orders, while Felipe could fill #99/11 = 9# orders, making a total of #9+11 = 20# orders if they both work.

So for both of them working to fill one order would take:

#99/20# hours.

To express in hours and minutes:

#99/20 = 80/20+19/20 = 4+(3*19)/(3*20) = 4+57/60#

That's #4# hours and #57# minutes, since a sixtieth of an hour is one minute.