You have a pack of nine cards numbered from one to nine.
You can split the cards into groups in many ways. For example, you could have 1, 2, 5 and 7 in one group, and 3, 4, 6, 8 and 9 in a second group. In this case the first group (1, 2, 5 and 7) adds up to 15 and the second group (3, 4, 6, 8 and 9) adds up to 30. So the second group totals twice the first group.
Now your challenge is to put the cards in two groups, one of four cards and the other five cards, so that one group totals three times the other group.
It may seem impossible, but there is a twist to it.
Answer at 9.00 on Monday