Puzzle 161
Can you fill the thermometers with mercury, such that the numbers outside the grid indicate how many cells in each row and column contain mercury.
Mercury always starts filling from the bottom of a thermometer and not every thermometer has to contain mercury.
Puzzle Copyright © Johan de Ruiter
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Hint
Tops of thermometers can't be filled unless the bottoms are.
Answer
Puzzle 162
My local greengrocer is a would-be mathematician.
She likes to arrange the apples in nice rows.
When she lays the apples in rows of 3, she has one left over.
And, when she lays them in rows of 5, she also has one left over.
Remarkably, she also has one left over when she arranges them in rows of 7 and 9.
But 11 seems to be the magic number, because in rows of 11 there are no apples left over.
How many apples does she have?
Puzzle Copyright © Kevin Stone
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Hint
There are fewer than 1,000 apples.
Answer
946 apples.
Reasoning
We know that (answer – 1) is divisible by 3, 5, 7, and 9.
If it's divisible by 9 then it's automatically divisible by 3.
So the number must be a multiple of 5, 7, and 9.
[5 x 7 x 9 = 315]
Since these numbers share no other common factors, we know that the answer must be a multiple of 315 (+1).
Let's try 1 x 315 + 1: 316 ÷ 11 = 28.73 – this doesn't work.
Let's try 2 x 315 + 1: 631 ÷ 11 = 57.36 – this doesn't work.
Let's try 3 x 315 + 1: 946 ÷ 11 = 86 – this works and is the answer.
Puzzle 163
In this puzzle, all of the numbers from 1 to 8 are used.
The differences between any two connected numbers are all different (larger - smaller).
Can you complete the grid?
Puzzle Copyright © Kevin Stone
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Hint
What are the possible differences?
Answer

Reasoning
The first observation is that all of the possible gaps must exist: 1, 2, 3, 4, 5, 6, 7, and let's call these Gap1, ..., Gap7.
Looking at Gap7, this can only happen when:
[Gap7a: 1 is next to 8]
Looking at Gap6, this can happen when:
[Gap6a: 1 is next to 7]
this is not allowed because 1 and 7 are given squares that are not next to each other.
[Gap6b: 2 is next to 8]
Looking at Gap5, this can happen when:
[Gap5a: 1 is next to 6]
[Gap5b: 2 is next to 7]
this is not allowed because [Gap6b: 2 is next to 8], which would mean that we can't also have [Gap7a: 1 is next to 8].
[Gap5c: 3 is next to 8]
this is not allowed because we couldn't then also have: [Gap7a: 1 is next to 8] and [Gap6b: 2 is next to 8].
We can't have the 8 above the 1, as there is then no place for [Gap6b: 2 is next to 8].
So, we have two possible places for the 8, to the left of the 1, or to the right of the 1.
8 to the left of 1

What can we place to the right of 1?
3 – no, because the gap between the 1 and 3, and the gap between 3 and 5, are both 2.
4 – no, because the gap between 4 and 5 is 1, which we already have.
6 – no, because the gap between 5 and 6 is 1, which we already have.
So the 8 can't go to the left of 1.
8 to the right of 1
We know [Gap5a: 1 is next to 6].
Let's try 6 to the left of 1. No matter where we place the 3 and 4 we end up with duplicate gaps. So this doesn't work.

So, the 6 must go above 1, but the 4 can't go to the left of 1 because of duplicate gaps. Therefore, this doesn't work either.

Which means that the final answer is:
Puzzle 164
Which are there more of:
...rolls in a dozen baker's dozen
or
...hours in a week?
Puzzle Copyright © Kevin Stone
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Hint
A baker's dozen is 13.
Answer
Hours in a week.
Reasoning
A dozen is usually 12, but a baker's dozen is usually 13.
So a dozen (12) baker's dozen (13) = 12 x 13 = 156.
There are 24 hours in a day, and 7 days in a week.
So there are 24 x 7 hours in a week = 168.
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