Agroup of college students are volunteering for 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

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.

B

walter needs to make at least 5 more cookies but no more than 40. 5 ≥ x ≥ 40;

step-by-step explanation:

walter has to make a minimum of 20 cookies. he already has 15 cookies made, so he must make 5 more to meet the minimum.

the maximum amount of cookies he can make is 55. he already has 15, so he has to make no more than 40 more cookies to meet the maximum.