Making numbers with 1, 2, 4 and 8
A child has four pieces of 1, 2, 4 and 8: rods in centimetres, weights for a balance, towers of cubes or bags of marbles, and each piece can be used once. Most questions ask which pieces make an exact amount, tapped on screen while a strip shows how much is still needed. Others name some of the pieces and ask for the missing one, or ask for the total.
Because each piece is double the one before, every number from 1 to 15 can be made in exactly one way. The reliable method is to start with the biggest piece and take each one that is not too big for what is left, which is also how binary numbers work.
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What changes each time
- Amounts from 3 to 15, always needing two or more pieces
- Rods, weights, towers of cubes or bags of marbles
- Which pieces, which one is missing, or how much altogether
More number sense and place value practice
- Tens and ones (Grade 1)
- Comparing numbers (<, = and >) (Grade 1)
- Hundreds, tens and ones (Grade 2)
- Odd and even numbers (Grade 2)
- Writing numbers in digits (Grade 3)
- Place value (Grade 3)
- Smallest and largest numbers (Grade 3)
- Rounding on a number line (Grade 3)
- Negative numbers on a number line (Grade 4)
- Halfway between two numbers (Grade 4)
- Nth largest and smallest numbers (Grade 5)