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Equation Builder gives you number tiles and operator tiles and asks you to build an expression that equals a target. Ten puzzles, with a bonus for speed. It runs the arithmetic backwards from how drills usually do — instead of computing an answer, you are searching for a route to one, which is a different and more interesting kind of thinking.
Read the target value for the puzzle.
Drag or tap number and operator tiles to build an expression.
The running value updates as you build.
Submit when your expression equals the target.
Ten puzzles; solving faster earns a speed bonus.
Number sense and inverse reasoning — working from an answer back to the operations that produce it. This is the skill behind estimating and behind sanity-checking a calculation, and it is much less practised than forward arithmetic.
Find the operation that gets you closest first, then fix the remainder with addition or subtraction.
Multiplication moves you a long way, addition moves you precisely. Use them in that order.
Check the parity of the target. If it is odd, at least one odd number has to survive to the end.
If you are one or two away, look for a tile you can add or subtract rather than rebuilding from scratch.
No. Reaching the target is what scores; unused tiles cost nothing.
Yes — multiplication and division bind tighter than addition and subtraction, the standard rule. The running total shows you the actual value as you build.
Yes. Every puzzle is generated from a known valid expression.
Countdown deals six numbers against a three-digit target and rewards near misses. This gives you a tile set and asks for an exact build.