The Broken Sum
- Explorers
- Levels 1 and 2
- Matchstick puzzle
Owl laid out a matchstick sum, but it’s wrong. Move just one stick to make it true.
Move one matchstick so the sum is true.
This one comes back on . You can solve it then, signed in.
Last set on . The answer stays inside Kiwimath, and here is why.
What the board shows
- As laid out, the sum reads 1 + 2 = 4, which is not true.
- There are 15 matchsticks on the table, and the same 15 must still be there after the move.
- You may move one stick, and only once.
How do matchstick puzzles work?
The sum is built from matchsticks, with each figure made the way a calculator shows it: seven places for a stick, like an 8 with every stick in place. The plus sign is two sticks, the minus sign one, and the equals sign two.
A move means picking up one stick and putting it down somewhere else. It can go back into the same figure, into a different figure, or into a sign. Nothing can be thrown away or added from outside.
After the move every figure has to be a proper digit and the sum has to be true. A child who finds a true sum can check the move by counting the sticks: there should be exactly as many as at the start.
What it trains: Number sense, careful checking and seeing digits as shapes.
Puzzles like this are part of olympiad preparation from the first classes. See the plan for Class 1 or Class 3.
What to ask while your child works
Questions like these keep a child thinking without giving anything away. They work for every puzzle of this kind.
- Can you read the sum aloud and say why it is not true?
- How many sticks does each figure use?
- After your move, did the number of sticks stay the same?
Warm up with one like The Broken Sum
This warm-up is not the puzzle above, and its answer is below. It is a different puzzle of the same kind, made for this page, so your child can practise before The Broken Sum comes back.
Move one matchstick so the sum is true.
See the warm-up answer
The sum becomes 5 + 1 = 6.
- Nine plus one is ten, which needs two figures. So either the 9 gets smaller or the plus becomes a minus. Try the 9 first.
- Take the top-right stick off the 9. What is left is a 5.
- Put that stick on the bottom left of the answer. The 5 there becomes a 6.
- Now it reads 5 + 1 = 6.
Questions parents ask about The Broken Sum
When can my child solve The Broken Sum?
The Broken Sum is due back as the Explorers puzzle of the week on Saturday 7 November 2026, opening at 6 PM India time. Your child can solve it then, signed in, with hints that open one at a time.
Who is The Broken Sum for?
It is an Explorers puzzle, for Levels 1 and 2, roughly Class 1 to 4. A younger child can try it with a grown-up reading the story aloud; the thinking matters more than the reading.