Puzzle 81
What day would tomorrow be if …
… yesterday was five days before the day after Sunday's tomorrow?
Puzzle Copyright © Kevin Stone
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Hint
Try working backwards.
Answer
Saturday.
Reasoning
It's best to work backwards:
"Sunday's tomorrow"
is Monday.
"the day after Sunday's tomorrow"
is therefore Tuesday.
"five days before the day after Sunday's tomorrow"
is therefore Thursday.
"yesterday was five days before the day after Sunday's tomorrow"
yesterday was Thursday, making today Friday. Therefore tomorrow is Saturday.
Puzzle 82
This BrainBashers safe has a rather unusual control panel.
In order to open the safe, you have to press every single square once only, in the correct sequence, ending on the square marked E.
Each square indicates which square to press next, for example, 2U means move up 2 squares and 3R means move right 3 squares.
Can you determine which square you must start with?
| 4R |
4D |
1R |
1D |
2D |
4L |
1D |
| 1R |
4D |
5D |
2R |
2D |
1L |
4L |
| 2R |
1D |
1L |
2R |
2R |
2D |
2U |
| 2R |
2R |
3U |
3D |
1R |
3U |
6L |
| 3U |
3R |
1D |
2U |
4L |
2D |
3L |
| 3U |
1L |
1R |
1R |
1R |
1R |
2U |
| 6U |
E |
2U |
2L |
4L |
1L |
2U |
Note: this puzzle is not interactive, and the safe buttons cannot be clicked.
Puzzle Copyright © Kevin Stone
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Hint
Start on any square, and see how far you can get.
Answer
Start from the 2U in the bottom right-hand corner.
Puzzle 83
Imagine a bottle recycling skip, empty other than one lonely bottle.
Every hour, on the hour, people come and put bottles into the skip.
The first hour, at noon, one person came and put a bottle in.
One hour later, two people each placed a bottle into the skip.
An hour later, four people each placed a bottle into the skip.
This doubling of people continued until 11pm, when the skip was finally full.
When was the skip exactly half full?
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Hint
Remember that the bottle count doubles each time.
Answer
10pm.
Reasoning
The skip started with 1 lonely bottle.
At Noon: 1 person came along and added a bottle, making the total 2 bottles.
At 1pm: 2 people came along and each added a bottle, making the total 2 + 2 = 4 bottles.
At 2pm: 4 people came along and each added a bottle, making the total 4 + 4 = 8 bottles.
At 3pm: 8 people came along and each added a bottle, making the total 8 + 8 = 16 bottles.
Therefore, the number of bottles in the skip is doubling every hour, as it was full at 11pm, it must have been half full at 10pm.
Puzzle 84
Which of the shapes is identical to the first one?
There might be more than one.
Puzzle Copyright © Robert A. Hartmann
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Hint
Try to rotate them around in your head, but watch out for mirror images.