What is a deductive numbers test?
A deductive numbers test gives you clues or constraints about unknown numbers, such as sums, differences, digits or divisibility, and asks you to work out the single value that satisfies all of them.
It sits between numerical reasoning and deductive reasoning: the maths is simple, but you must combine the constraints logically and rule out every alternative. Shape equations, digit puzzles and age problems are common formats.
By What's Your IQ · Published 4 Oct 2026 · Updated 4 Oct 2026- Format
- 2–4 clues about unknowns, then 4 numeric options
- Question types
- Shape equations, digit puzzles, constraint puzzles
- Typical employer test
- 15–25 items in 15–25 minutes
- Measures
- Combining constraints, number sense, checking
- This test
- 10 puzzles, 10 minutes, free, worked answers
Shape equations, one step at a time
Start with the line that has only one unknown. Each value you find unlocks the next line.STEP 1 · ONE UNKNOWNLine 1 only has circles. Two circles make 10, so one circle is 5.
Six shortcuts that eliminate fast
You rarely need full algebra. These checks usually cut four options to one.Take the test
10 puzzles · 10 minutes · scratch paper allowed, no calculator neededEquations5 puzzles: shapes, ages, sumsDigit puzzles3 puzzlesConstraints2 puzzles
WORK BACKWARDS
The answer is already on the screen
With four options, testing each against the clues is often faster than solving. Pólya called this "working backwards". Start with the clue that rejects the most options.
Example: a 2-digit number, digits sum to 11, tens digit is 3 more than units. Options 47, 83, 74, 65.
47
83
74
65
Keep going
References
- Pólya, G. (1945). How to Solve It: A New Aspect of Mathematical Method. Princeton University Press.
- Rips, L. J. (1994). The Psychology of Proof: Deductive Reasoning in Human Thinking. MIT Press.