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Puzzles

12 December

Put the digits 1 to 9 (using each digit exactly once) in the boxes so that the sums reading across and down are correct. The sums should be read left to right and top to bottom ignoring the usual order of operations. For example, 4+3×2 is 14, not 10.
+-= -2
- - -
+÷= 4
+ ÷ ×
+×= 50
=
4
=
-4
=
10
The answer is the product of the digits in the red boxes.

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Tags: numbers, grids

11 December

This year, I was involved in starting Chalkdust Magazine. One of my roles for the magazine has been writing the £100 crossnumber puzzle.
What is the answer to 35 across in the first issue's crossnumber?

35A. The smallest number which is one more than triple its reverse. (3)

10 December

This number is divisible by 2. One more than this number is divisible by 3. Two more than this number is divisible by 5. Three more than this number is divisible by 7. Four more than this number is divisible by 11. Five more than this number is divisible by 13.

8 December

What is the largest number of factors which a number less than a million has?

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7 December

In September, my puzzle appeared as Alex Bellos's Monday Puzzle. The puzzle asked what the highest rugby score was which can only be made with one combination of kicks, tries and converted tries.
What is the highest rugby score which can be made with 101 different combinations of kicks, tries and converted tries?

6 December

Put the digits 1 to 9 (using each digit once) in the boxes so that the three digit numbers formed (reading left to right and top to bottom) have the desired properties written by their rows and columns.
multiple of 5
multiple of 7
cube number
multiple of 9multiple of 3multiple of 4
Today's number is the multiple of 5 formed in the first row.

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Tags: numbers, grids

4 December

Put the digits 1 to 9 (using each digit exactly once) in the boxes so that the sums reading across and down are correct. The sums should be read left to right and top to bottom ignoring the usual order of operations. For example, 4+3×2 is 14, not 10.
-+= -4
+ + +
-÷= -1
- ÷ ×
-×= -30
=
0
=
2
=
54
The answer is the product of the digits in the red boxes.

Show answer

Tags: numbers, grids

Santa

Each of the letters D, A, Y, S, N, T, B, R and E represents a different non-zero digit. The following sum is true:
$$ \begin{array}{cccccc} D&A&D&D&Y\\ B&E&A&R&D&+\\ \hline S&A&N&T&A \end{array} $$
This has a unique solution, but I haven't found a way to find the solution without brute force. This less insightful sum is also true with the same values of the letters (and should allow you to find the values of the letters using logic alone):
$$ \begin{array}{ccccc} R&A&T&S\\ N&E&R&D&+\\ \hline S&A&N&E \end{array} $$

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