Question

Kathy can clean 12 house in 10 hrs. If she goes at a steady pace. How many hrs. will it take her to clean 27 houses?

Answer 1

To solve this, set up a proportion with X being our unknown. If she cleans 12 houses in 10 hours, she cleans 27 houses in X hours. It will look like $\frac{12}{10} = \frac{27}{x}$.

Now cross-multiply to get 12x = 27(10) or 12x = 270. Divide by 12 on both sides to isolate x, X = 22.5.

It will take Kathy 22.5 hours to clean 27 houses. Must be some pretty small houses. 

Answer 2

12 houses/10 hours=1.2 house per hour
27 houses/1.2 houses per hour=22.5 hours