Bunuel wrote:

A painting crew painted 80 houses. They painted the first y houses at a rate of x houses per week. Then more painters arrived and everyone worked together to paint the remaining houses at a rate of 1.25x houses per week. How many weeks did it take to paint all 80 houses, in terms of x and y?

A. (320 - y)/(5x)

B. (y +320)/(5x)

C. 5(80 - y)/(4x)

D. (y + 400)/(4x)

E. (4y + 320)/(5x)

Kudos for a correct solution.

Painted first y houses @x houses per week

To paint 1 house, time taken=1/x weeks

Therefore, to paint y houses, time taken=y/x weeks

Similarly, time taken to paint 80-y houses=80-y/1.25x

Total time taken=y/x+80-y/1.2x=4(0.25y+80)/5x=y+320/5x

Answer B