You may also like

Double Digit

Choose two digits and arrange them to make two double-digit numbers. Now add your double-digit numbers. Now add your single digit numbers. Divide your double-digit answer by your single-digit answer. Try lots of examples. What happens? Can you explain it?

Repeaters

Choose any 3 digits and make a 6 digit number by repeating the 3 digits in the same order (e.g. 594594). Explain why whatever digits you choose the number will always be divisible by 7, 11 and 13.

Big Powers

Three people chose this as a favourite problem. It is the sort of problem that needs thinking time - but once the connection is made it gives access to many similar ideas.

More Mathematical Mysteries

Age 11 to 14 Challenge Level:

Write down a three-digit number

Three chickens.

Change the order of the digits to get a different number

Find the difference between the two three digit numbers

Add together the digits of your answer. If you arrive at a two-digit answer, add the two digits to reduce your answer to a single digit answer

Subtract $5$ from the number you have

Find that equivalent number letter in the alphabet (1=A, 2=B etc.)

Name a country that begins with letter

Anteater.

Using the second letter of the name of the country that you chose, name a jungle animal that starts with that letter.

Name the colour of that animal.

Using the final letter of the name of the country that you chose, name a different animal that starts with that letter.

Name a fruit that starts with the last letter of that animal's name.

Melon slice.

Did you end up with orange or apple?

How did I know?