Ricardo's old toaster can hold at most two slices of bread and toast them on one side at a time. He wants his bread toasted on both sides and buttered on one side.
It takes:
- 3 seconds to put each slice into the toaster and,
- 30 seconds to toast one side of 1 or 2 slices and,
- 3 seconds to reverse a slice and,
- 12 seconds to butter one side (that side must already be toasted).
- 3 seconds to remove a slice from the toaster without putting it back in reverse.
Assuming that, only one of these
operations can be done at a time:
In how short a time can Ricardo toast and butter three slices?
1. Load slices A and B into toaster: 6 seconds.
2. Toast them : 30
3. Reverse slice A : 3
4. Remove slice B : 3
5. Place slice C in toaster : 3
6. Toast : 30
7. Reverse slice C : 3
8. Remove slice A : 3
9. Reload slice B for opposite side: 3
10. Toast : 30
11. Butter each desired side : 36
---------
150 sec. = 2.5 min.
|
|
Posted by Charlie
on 2013-05-13 13:35:00 |
solution
