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Working Systematically - Challenges
Reach 100
Age 7 to 11
Challenge Level 
Choose four different digits from 1-9 and put one in each box so that the resulting four two-digit numbers add to a total of 100.
Sticky Numbers
Age 11 to 14
Challenge Level
Can you arrange the numbers 1 to 17 in a row so that each adjacent pair adds up to a square number?
ACE, TWO, THREE...
Age 11 to 14
Challenge Level
Can you picture how to order the cards to reproduce Charlie's card trick for yourself?
Two and Two
Age 11 to 16
Challenge Level
How many solutions can you find to this sum? Each of the different letters stands for a different number.
Product Sudoku
Age 11 to 16
Challenge Level
The clues for this Sudoku are the product of the numbers in adjacent squares.
Pair Sums
Age 11 to 14
Challenge Level
Five numbers added together in pairs produce: 0, 2, 4, 4, 6, 8, 9, 11, 13, 15 What are the five numbers?