Question

a group of college students are volunteering for help the homeless during spring break. They are putting the finishing touches on a house they built. Working alone, irina can paint a certain room in 4 hours. Paulo can paint the same room in 3 hours. write an equation that can be used to find how long it will take them working together to paint the room. how many hours will it take them to paint the room?
A.12 hours
B.1.71 hours
C.0.14 hours
D.3.5 hours

Answer 1

Let us say that x is the total amount of time it will take if they work together.

From the given statement above, we know that the rate of Irina working alone is 1 job / 4 hours. While that of Paulo is 1 job / 3 hours. Where 1 job indicates to the job of completely painting the room. So adding the two rates would result in 1 job / x hours. Therefore:

1 / 4 + 1 / 3 = 1 / x

Multiplying both sides with 12 x:

(1 / 4 + 1 / 3 = 1 / x) 12 x

3 x + 4 x = 12

7 x = 12

x = 1.71 hours

So working together, they can paint the room for 1.71 hours.

 

Answer:

B