Question 266025
Let x=amount of time needed to paint the house when both are working together
Then together they paint at the rate of 1/x house per hour

Jack paints at the rate of 1/30 house per hour
Trainee paints at the rate of 1/45 house per hour
Together they pain at the rate of 1/30 + 1/45 house per hour
So, our equation to solve is:
1/30 + 1/45=1/x  multiply each term by 90x
3x+2x=90
5x=90
x=18 hours----------------------------time needed when both are working togeether

CK
(1/30)*18 + (1/45)*18 needs to equal 1
54/90 + 36/90=1
1=1

Hope this helps---ptaylor