How much time would it take both presses to do the one job?

Question

A printing press can produce 1 day’s newspaper in 4 hours. A higher-speed machine can do 1 day’s newspaper in 2 hours. I don’t know where to start .

Answer 1

t represents the time working together

(t / 4) + (t / 2) = 1

t + 2t = 4

3t = 4

t = 1 1/3

The presses work for 1 1/3 hour or 1 hour 20 minutes.

Answer 2

1/4 + 1/2 = 1/b

multiply by 4b

b +2b = 4

3b = 4

b = 4/3 = 1 and 1/3 hour working together

first does 1/4 the job in 1 hour

2nd does 1/2 the job in 1 hour

together they do 1/b of the job in 1 hour

1/4 +1/2 = 1/b in one hour for both

3/4=1/b

b=4/3=1 1/3

b = 1 hour and 20 minutes