"work" word problem?

Question

One printing press can print 4000 copies in an hour and another press can print 3000 copies in an our. after the first press has been running for 3 hours, the second press is stared. how soon after the start of the second press will 50,000 copies be printed?

please show algebraically

Answer 1

let x equal the number of hours after the second press has been started.

first press = 4000 cph
second press = 3000 cph

3(4000) + x(4000+3000) = 50000

12000 + 7000x = 50000

7000x = 38000

x = 38000/7000

x = 38/7

x = 5 3/7 hours

convert 3/7 hours into minutes and seconds. (multiply by 60, the whole numbers equal the minutes, decimal must then be converted to seconds by multiplying by 60.

5 hours 25 minutes ~43 seconds

Answer 2

50,000 - (4000 x 3) = 38,000

38,000 = 4000x + 3000x

38000 = 7000x

x = 38000/7000

Answer 3

4000 * 3 = 12000
50,000 - 12,000 = 38,000

Now, you want to find

4000n + 3000n = 38,000
7000n = 38,000
n= 5.43 hours (38000/7000 not exactly 5.43)


4000(5.43) + 3000(5.43) = 38010

And add the 12000 to that, which equals 50000