Jack can paint a house in 5 days, and Richard can paint the same house in 7 days. Working together, how long will it take them to finish the job?
Answer (3)
Well, their speeds are ( V 1 is Jack's speed, and V 2 is Richard's. V 1 = 5 1 h o u ses / d a y V 2 = 7 1 h o u ses / d a y V = V 1 + V 2 = 5 1 + 7 1 = 35 7 + 5 = 35 12 They, together, can paint 12 houses in 35 days. To get a single house, we only have to calculate 12 35 which is very close to 3 (a bit below)
In 7*5 = 35 days, Jack can paint 7 houses.
In 5*7 = 35 days, Richard can paint 5 houses.
So in 35 days, the two of them can paint 12 houses. To paint just one house, they'll need 1/12 the time, or 35/12 = 2 11/12 days. ;
Jack and Richard can paint the house together in approximately 2.92 days. Their combined work rate results in them completing the house by working simultaneously. This calculation is based on their individual rates, which are added to find the total efficiency.
;
