Question

You need to make 5 grilled cheese sandwiches. You have a grill that is large enough to toast 2 sandwiches at a time. The sandwiches must be toasted one minute on each side. It takes 3 seconds to flip a sandwich and 5 seconds to take one off or put one on the grill. What is the shortest amount of time needed to toast all five sandwiches?

Answer 1

2 sandwiches -
4 minutes to toast
6 seconds to flip
20 seconds to take off or put on
4 minutes and 26 seconds

4 sandwiches
8 minutes and 52 seconds

last sandwich
2 minutes to toast
3 seconds to flip
10 seconds to take off or put on
2 minutes and 13 seconds

total: 10 minutes 65
11 minutes and 5 seconds

Answer 2

Each sandwich is toasted for 2 minutes and it takes 3 seconds to flip it.
The first two sandwiches will be toasted in 2 minutes (toasting) and 6 seconds (flipping).
The two will then be switched which will take 10 seconds.
The next two will again take 2 minutes and 6 seconds.
The final sandwich will take 5 seconds to be placed.
The final sandwich will also take 2 minutes to toast and 3 seconds to flip.
Total time:
2 + 2 +2 = 6 minutes
6 + 10 + 6 + 3 = 25 seconds
Total time is 6 minutes and 25 seconds.