Sum Fold
Six numbers, one target, four operations. Fold them together until they land exactly.
Sum Fold gives you six numbers and a three-digit target. Combine any two numbers with +, −, × or ÷ and the result replaces them both. Keep folding numbers together until one of them is exactly the target.
Every intermediate value must be a positive whole number — no fractions, no negatives — which is the constraint that makes the puzzle solvable in your head rather than with a calculator.
How to play
- Tap a number to select it.
- Tap an operation — plus, minus, times or divide.
- Tap a second number. The two are consumed and their result joins the row.
- Repeat until one of your numbers matches the target exactly.
Undo steps back one operation; Start over resets the whole board.
Where to begin
The instinct is to look at your six numbers and start combining. That is almost always slower than looking at the target first.
Ask what the target sits near. If it is 428, then 400 is the obvious neighbourhood, and 400 comes from 50×8 or 100×4. Now you have a much smaller question: can the remaining numbers make 28? That decomposition — big jump, then small correction — solves the majority of puzzles in three or four steps.
Division deserves more respect than most players give it. It is the only operation that makes numbers smaller in a controlled way, and a well-chosen division frequently turns an ugly leftover into exactly the small number you needed.
Par, and beating it
Each puzzle is built forwards from a real chain of operations, so a solution is guaranteed to exist and its length is the par. Finding a shorter chain than the generator used is entirely possible and is the most satisfying outcome the game offers.
Stuck? The answer and hints page walks through one working solution.
Tips
- Start from the target, not the numbers. Ask what the target is close to — a round hundred, a multiple of 25 — and work out which product could get you into that neighbourhood.
- Multiplication moves you a long way and addition moves you a little. Use the big jump first and save the small numbers to close the last gap.
- Division is the move people forget. When the target is awkward, a division that produces a clean small number often unlocks the whole chain.
- You never have to use all six numbers. A three-step solution using four of them beats a five-step scramble that uses everything.
Questions
Do I have to use every number?
No. Use as many or as few as you like. Each number can only be used once, but leaving two untouched is completely normal — most solutions use four.
Are fractions and negative numbers allowed?
No. Every intermediate result must be a positive whole number, so a division only works when it divides exactly. This is what keeps the puzzle solvable by hand.
What is par?
The number of operations in the solution the puzzle was built from. Beating par is possible — it just means you found a shorter route than the generator did.
Is every puzzle solvable?
Yes. The puzzle is constructed forwards from a real chain of operations, so at least one exact solution always exists before the puzzle is ever shown.
Does everyone get the same numbers?
Yes, the puzzle is derived from the date. Everyone plays the same set worldwide, and it changes at midnight UTC.