whats the answer
A PAINTER CAN FINISH PAINTING A HOUSE IN 7 HOURS.HER ASSISTANT TAKES 9 HOURS TO FINISH THE SAME JOB. HOW LONG WOULD IT TAKE THEM TO COMPLETE THE JOB IF THEY WERE WORKING TOGETHER
A painter who can paint a house in 7 hrs can paint 1/7 of the house in 1 hour.
An assistant who can paint the same house in 9 hrs can paint 1/9 of the house in 1 hour.
Painting at the same time, for x hrs, the painter can paint x/7 of the house,
and the assistant can paint x/9 of the house. Adding those portions together
results in 1 house being painted.
x/7 + x/9 = 1
Multiply by 63 (7 * 9) to get rid of the fractions.
63 * (x/7 + x/9) = 1 * 63
9x + 7x = 63
16x = 63
x = 63/16 hrs or 3.9375 hrs
3.9375 / 7 = 0.5625 of the house
3.9375 / 9 = 0.4375 of the house
0.5625 + 0.4375 = 1 house