Aon-style drills
Aon-style switch deduction (switchChallenge)
Work out which code turned one row of symbols into another, open-ended for 6 minutes
Used by Morgan Stanley (Reported), BNP Paribas (Unverified), Schroders (Official)
The format
- Time6 minutes on one countdown
- Each itemFour symbols in, four out, and three codes to choose from
- CodesDigit 1 says which symbol comes out first, and so on
- ItemsNo set number, harder after right answers and easier after wrong ones
- Scoring+1 right, −1 wrong
- Have readyNothing, as it's all done in your head
How to approach it
- Find where the first output symbol came from, then check every other place
- On chained items, work out the middle row before looking at the options
- A wrong answer costs a point and a level, so don't guess
More optionsExtra time, practice, shortcuts
- Untimed practice firstOne untimed practice item you can repeat
- Keyboard shortcuts
Single-key shortcuts can clash with some screen readers, so switch them off if they get in the way
Format notes
What this drill copies from the published format and how sure we are of each value, checked 22 September 2026
| Parameter | Value | Label |
|---|---|---|
| Total time | 6 minutes on one countdown | OfficialSource 1 for Total timeSource 2 for Total time |
| Items | No set number: a new one after each answer | OfficialSource for Items |
| Rows | 4 symbols in and 4 symbols out | OfficialSource for Rows |
| Code options | 3 per item | OfficialSource for Code options |
| What a code means | Digit k says which position lands in place k, so 1234 changes nothing | OfficialSource for What a code means |
| Chained codesChains are official, and both of the provider's chained examples show the given code above the options; the level they start at is our choice | Two codes in a row from level 6, with the first one shown | OfficialSource for Chained codes |
| Three codes in a rowOne prep site reports up to three layers | From level 9 | UnverifiedSource for Three codes in a row |
| Wrong codesTaken from the provider's worked examples | Share 0, 1 or 2 places with the right code | OfficialSource for Wrong codes |
| DifficultyThe provider itself only says items may get harder, and the size of each step is our choice | One level up after a right answer and one down after a wrong one | ReportedSource 1 for DifficultySource 2 for Difficulty |
| SymbolsThe provider's symbols are coloured; ours are one colour, so shape alone carries the meaning | Four different shapes per row | OfficialSource for Symbols |
| AnsweringWhether the real test has a separate confirm button is unclear | Choose a code and the next item appears, with no confirm step | UnverifiedSource for Answering |
| Going backThe provider doesn't describe a way back, so forward only is our reading | Not possible: answer and the next one appears | Unverified |
| Wrong answers | Usually cost points | OfficialSource for Wrong answers |
| ScoringThe size of the deduction is our reading, and there are no blanks as every item needs an answer to go on | +1 for a right answer, −1 for a wrong one | UnverifiedSource for Scoring |
| LevelsAnecdotally, top Morgan Stanley candidates pass level 40, but our levels step differently and stop getting harder at level 9, so the numbers don't compare | Your highest level is shown at the end | ReportedSource for Levels |
| Before the testRepeats here alternate between a single code and a chain of two, which is our choice | One practice item you can repeat, then a summary page | OfficialSource 1 for Before the testSource 2 for Before the test |
| PausingEnd test is here for practice only | Not possible, and the test ends itself when time is up | OfficialSource for Pausing |
| Morgan Stanley | 6 minutes, not sent to every candidate | ReportedSource 1 for Morgan StanleySource 2 for Morgan StanleySource 3 for Morgan Stanley |
| BNP ParibasTwo pages from one prep site, around 2024 and 2026 | Practice for it bundled with the logical test, or listed with a verbal test for global markets | UnverifiedSource 1 for BNP ParibasSource 2 for BNP Paribas |
| SchrodersWhether spring applicants sit it is unconfirmed | Named in its internship and placement assessments | OfficialSource for Schroders |
Independent practice in the style of Aon's published format. Not affiliated with or endorsed by Aon