Problema Solution
One maid can clean the house in 4 hours. Another maid can do the job in 7 hours.how long will it take them to do the job working together?
Answer provided by our tutors
Maid A can clean 1/7 of the house in 1 hour.
Maid B can clean 1/4 of the house in 1 hour.
Between them, they can clean 11/28 of the house in 1 hour.
They can clean 1/28 of the house in 1/11 of an hour.
They can clean 28/28 (all) of the house in 28/11 hours, or about 2.55 hours.
They can clean the house in 2 hours and 33 minutes.
Here's another way to look at it.
A. 1/11=5.5 minutes
B. 28/3=9 hours 20 minutes
C. 28/11=2 hours 33 minutes
D. 1/28=2.1 minutes
A and D are too fast, and even the slow maid can clean faster than choice B. Therefore, C is the only plausible answer.