Jerry has to walk to the sink / recycling bin 28 cans / 4 cans per trip = 7 trips. The round trip takes 10 seconds per way * 2 ways = 20 seconds. Counting the time he spent pouring out the cans and the time the round trip took, he spent 20 seconds per trip + 30 seconds per trip = 50 seconds per trip. With 7 round trips, he spent 50 seconds per trip * 7 trips = 350 seconds.
This justifies what answer for what question? Q & A:
Jerry has a bunch of half-empty soda cans on his desk. He needs to drain all of them and put them in the recycling bin. He can carry four cans at once, and it takes him 30 seconds to drain those 4 cans. It takes him ten seconds each way to walk to the sink and recycling bin and then back to his desk. If there are 28 cans on Jerry's desk, how long does it take him to throw all of them away?
350