You may also like

Digit Sum

What is the sum of all the digits in all the integers from one to one million?

Eight Dominoes

Using the 8 dominoes make a square where each of the columns and rows adds up to 8

Two and Two

How many solutions can you find to this sum? Each of the different letters stands for a different number.

Postage

Age 14 to 16 Challenge Level:

image of stampThe country Sixtania prints postage stamps with only three values 6 lucres, 10 lucres and 15 lucres (where the currency is in lucres).

Which values cannot be made up with combinations of these postage stamps? Prove that all other values can be made up.