Question

One printing press can print 5,000 advertising cards in 12 seconds. Another printing press can print the same number of cards in 7 1 2 seconds. If both presses are used together to print the 5,000 cards, how many seconds will it take them?

same with this one but i tried an ide and got 54 second is this right if not can you show solution

Answer 1

first one 5000/12 cards/s
second one 5000/7.5cards/s

together (5000/12 + 5000/7.5) cards/s
so
(5000/12 + 5000/7.5) t = 5000 cards
(1/12 + 1/7.5) t = 1

.217 t = 1
t = 4.62 seconds

clearly they do NOT take more time working together than either takes alone so it HAS to be less than 7.5 seconds.