Puzzles

Arrange the digits 1-9 in a 3×3 square so: each digit the first row is the number of letters in the (English) name of the previous digit, each digit in the second row is one less than the previous digit, each digit in the third row is a multiple of the previous digit; the second column is an 3-digit even number, and the third column contains one even digit. The number in the first column is today's number.

There is a row of 1000 closed lockers numbered from 1 to 1000 (inclusive). Near the lockers, there is a bucket containing the numbers 1 to 1000 (inclusive) written on scraps of paper.

1000 people then each do the following:

Today's number is the number of lockers that will be closed at the end of this process.

Write down the numbers from 12 to 22 (including 12 and 22). Under each number, write down its largest odd factor*.

Today's number is the sum of all these odd factors.

I make a book by taking 111 sheets of paper, folding them all in half, then stapling them all together through the fold. I then number the pages from 1 to 444.

Today's number is the sum of the two page numbers on the centre spread of my book.

Today's number is the number of 0s that 611! (611×610×...×2×1) ends in.

Put the digits 1 to 9 (using each digit exactly once) in the boxes so that the sums 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. Today's number is the product of the numbers in the red boxes.

Today's number is the area of the largest dodecagon that it's possible to fit inside a circle with area \(\displaystyle\frac{172\pi}3\).

There are 5 ways to write 4 as the sum of 1s and 2s:

Today's number is the number of ways you can write 12 as the sum of 1s and 2s.