marta can vacuum the house in 50 minutes. it takes her daughter 1 hr and 15 minutes to vacuum the house. how long would it take them if they worked together

Answer 1

Let's assume the house if 1000 ft² (It doesn't matter what you use as long as it is reasonable!)

So, Marta can vaccum 1000 ft²/50 minutes = 20 ft² minute

for the daughter 1000 ft²/75 minutes = 13.33 ft² minute

So, together, they can vacuum 33.33 ft² per minute

Therefore, 1000 ft²/(33.33 ft²/minute) = 30 minutes