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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.

Alphabet Soup

Age 11 to 14
Challenge Level

This challenge is to make up YOUR OWN word-arithmetic challenge.

Each letter represents a digit and where the same letter appears more than once it must represent the same digit each time.

The hard part is to make up some message rather than just using any old letters. Send in your word-arithmetic challenge, together with at least one solution to it.

Another challenge is to discover if the puzzle has just one solution or many. Here are two easy examples; they are just addition sums and you may be more inventive and make up subtractions, multiplications or divisions:
 

  N R I C H
+ S T A R S
  M A T H S
 
  M A T H
+ E M A T
  I C A L

Lastly, can you prove that

  N R I C H
+ M A T H S
  S T A R S

cannot be made to work?