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Have a look at this grid:
Can you see how it has been made?
Why is the 60 in that particular square?
Why does 20 appear twice?
In the interactivity below, some of the grid is filled in for you.
Can you work out which number goes in each row and column heading?
Once you know what each heading must be, drag the purple numbers to the appropriate spaces. When you think you have cracked it, click "Show the solution" to see if you are right.
Andrew decorated 20 biscuits to take to a party. He lined them up and put icing on every second biscuit and different decorations on other biscuits. How many biscuits weren't decorated?
You can make a calculator count for you by any number you choose. You can count by ones to reach 24. You can count by twos to reach 24. What else can you count by to reach 24?
Follow the clues to find the mystery number.