Numerical reasoning test
Find the logic behind a sequence of numbers and fill in the missing one. Only digits are used, so it works in every language.
Try real example questions
These are the same worked examples shown before the section in the test. Pick an answer, then press “Explain” to step through the solution.
What number series measure
Number series test quantitative reasoning: seeing relationships between numbers and extending them. It's not about calculation speed or school maths; the arithmetic is simple, but the pattern has to be discovered.
Common sequence rules
- Constant difference: 4, 7, 10, 13 … (+3 each time).
- Constant ratio: 3, 6, 12, 24 … (×2 each time).
- Growing differences: 2, 3, 5, 8, 12 … (+1, +2, +3, +4).
- Alternating operations: +5, −2, +5, −2 …
- Interleaved series: every other number belongs to a second sequence.
- Each term from the previous ones: 1, 1, 2, 3, 5, 8 … (the sum of the two before).
A reliable method
- Write the differences between neighbours.
- If they aren't constant, look at the differences of the differences, or at ratios.
- Try splitting the sequence into odd and even positions.
- Check whether each number depends on the one or two before it.
- Confirm the rule on every number shown before choosing an answer.
In the IQ Atlas test
12 questions from simple steps to sequences built on sums of previous terms. Every question is checked so that only one rule fits the numbers shown, so there's never a second defensible answer.
Frequently asked questions
Are number series a fair test across countries?
Digits are shared almost worldwide and the arithmetic is basic, which makes number series one of the most language-independent ways to measure quantitative reasoning.