TheGmatTutor wrote:

Hi all,

I have a couple questions regarding the work problems below. I know how to solve these through plugging in numbers or using the answer choices, but how would you solve these algebraically?

1.Working together, printer A and printer B would finish the task in 24 minutes. Printer A alone would finish the task in 60 minutes. How many pages does the task contain if printer B prints 5 pages a minute more than printer A ?

a. 600

b. 800

c. 1000

d. 1200

e. 1500

answer:

2. A pool can be filled in 4 hours and drained in 5 hours. The valve that fills the pool was opened at 1:00 pm and some time later the drain that empties the pool was also opened. If the pool was filled by 11:00 pm and not earlier, when was the drain opened?

a. at 2:00 pm

b. at 2:30 pm

c. at 3:00 pm

d. at 3:30 pm

e. at 4:00 pm

answer:

3.It takes printer A 4 more minutes than printer B to print 40 pages. Working together, the two printers can print 50 pages in 6 minutes. How long will it take printer A to print 80 pages?

a. 12

b. 18

c. 20

d. 24

e. 30

answer:

I think you should have posted all these questions in separate threads. Anyways, I will take a stab at the first question:

A + B --> 24 minutes

A = p / min

B = p + 5 / min

A + B will both produce pages in 24 minutes = 24p + 24(p+5) = 48p + 120

Total pages = 60p (As it takes A 60 minutes to finish the task)

Thus,

48p + 120 = 60p

p=10

Total pages = 10*60 = 600

Answer: A

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