Question

A group of college students is volunteering for Homes for the Community during their springbreak.They are putting the finishing touches on a house they built.Working alone, Wade can paint a certain room in 3 hours. Rhonda can paint the same room in 7 hours. How long will it take them working together to paint the room? Round your answer to the nearest hundredth.

Answer 1

Okay, so the rate is 1 job / hours, so:
1/3 + 1/7 (This covers both their work rates) = 1/n (n represents the time it take for them to work together)
Get the LCD:
7/21+ 3/21 = 1/n
10/21 = 1/n
Cross multiply:
10n = 21
n = 2.1 
It will take them 2.1 hours, or 2 hours and 6 minutes