Problema Solution
Patrice, by himself, can paint four rooms in 10 hours. If he hires April to help, they can do the same job together in 6 hours. If he lets April work alone, how long will it to take her to paint 4 rooms?
Answer provided by our tutors
If person 1 does a job in a hours and person 2 does a job in b hours, then they can do the job together in a*b/(a+b) hours. In this particular problem, you know Patrice can do the job in 10 hours, so a=10. You don't know b, but you know a*b/(a+b)=6 and you know a is 10.
10b/(10+b)=6
Multiply both sides of the equation by (10+b)
10b=6*(10+b)
10b=60+6b
4b=60
b=15
It would take April 15 hours to paint the four rooms herself.