Blog

1. The square number larger than 1 whose square root is equal to the sum of its digits.
2. The smallest square number whose factors add up to a different square number.
3. The largest number that cannot be written in the form \(23n+17m\), where \(n\) and \(m\) are positive integers (or 0).
4. Write down a three-digit number whose digits are decreasing. Write down the reverse of this number and find the difference. Add this difference to its reverse. What is the result?
5. The number of numbers between 0 and 10,000,000 that do not contain the digits 0, 1, 2, 3, 4, 5 or 6.
6. The lowest common multiple of 57 and 249.
7. The sum of all the odd numbers between 0 and 66.
8. One less than four times the 40th triangle number.
9. The number of factors of the number \(2^{756}\)×\(3^{12}\).
10. In a book with 13,204 pages, what do the page numbers of the middle two pages add up to?
11. The number of off-diagonal elements in a 27×27 matrix.
12. The largest number, \(k\), such that \(27k/(27+k)\) is an integer.

                        

You might also enjoy...

Christmas card 2024

Christmas card 2023

Christmas card 2017

Christmas card 2022

Comments

 2016-12-20 

@Matthew: Thank you for the prompt response! It makes sense now and perhaps I should have read a little closer!

Dan Whitman

                 

 ⭐ top comment (2016-12-20) ⭐ 

@Dan Whitman: Find the difference between the original number and the reverse of the original. Call this difference \(a\). Next add \(a\) to the reverse of \(a\)...

Matthew

            ×1     

 2016-12-20 

In number 4 what are we to take the difference between? Do you mean the difference between the original number and its reverse? If so when you add the difference back to the reverse you simply get the original number, which is ambiguous. I am not sure what you are asking us to do here.

Dan Whitman