IMC 24-in-18: Free Number Sequence Test Replica
"24 in 18" is the candidate nickname for IMC's number-sequence screen: roughly 24 sequence questions in 18 minutes, multiple choice, no calculator, with difficulty that ramps up sharply in the back half. Take a full generated run below in the same shape, get a score, and see which pattern families cost you points. No signup.
What the 24-in-18 actually is
Candidates who sit IMC's online assessment consistently describe a dedicated number-sequence module of about 24 questions with an 18-minute clock, which is where the "24 in 18" nickname comes from. Each question shows a short sequence and asks for the next term from five options. There is no calculator, and unlike Optiver's 80 in 8 there is no penalty for a wrong answer, so an educated guess always beats a blank.
The defining feature is the ramp. The first third is plain arithmetic and geometric progressions that most candidates clear in seconds. The middle third mixes in interleaved sequences, recurrences and difference ladders. The final third is where reports say the screen is actually decided: fraction sequences whose numerators and denominators follow separate rules, repeating operation cycles, and power towers. This replica follows the same ramp. For the wider process around this module, see the IMC online assessment guide and the IMC interview process overview.
The format, as reported
How to read a sequence fast
Sequence screens reward a fixed checklist, not inspiration. Run these checks in order and commit to the first rule that fits every gap:
- Check growth first: differences, then ratios. Write the gaps between terms. Constant gaps mean arithmetic; gaps that grow by a constant mean a second-difference rule; if gaps explode, divide neighbours and look for a constant ratio like 2, 3 or 1.5.
- Then check interleaving. If nothing fits, read the odd positions and the even positions as two separate sequences. A messy sequence that alternates up-down is almost always two clean ones braided together.
- Then try known ladders: squares, cubes, primes, Fibonacci. Differences of 1, 4, 9, 16 or 2, 3, 5, 7 or 1, 1, 2, 3, 5 are the standard hard-question skeletons, and so are recurrences where each term combines the two before it.
- Digit tricks last. Digit sums, reversals and concatenations are rare and expensive to test, so only reach for them when every structural rule has failed. On fractions, treat numerator and denominator as two separate sequences before you try to reduce anything.
For the taxonomy behind this checklist with worked examples, see number sequence tests in trading interviews. When the sequences feel solid, build out the rest of your IMC prep:
How this replica works
Every run is generated fresh in your browser from the eight pattern families above, on the same easy-to-hard ramp candidates describe. Each question's correct option is computed from the generating rule itself, and the page re-derives every answer from the rule before showing it to you, so the option marked correct always is. If you have sat a recent IMC sequences screen and something here is off, tell us at [email protected].