How the Number Differences test works
A digit from 1 to 9 appears in the middle of the screen and disappears after about two seconds. When the next digit appears, you type the difference between it and the one before on the number pad. The answer is always positive, so 3 then 7 and 7 then 3 both give 4. Your answer brings up the next digit, and you cannot change it once typed.
Candidates report that the gap is always 1 to 4, and that there are eight rounds of about two minutes each. It opens the ATSA at a Pearson VUE test centre, on a desktop keyboard. This section is reported to start with a practice round you can repeat, with the same digits each time.
How to answer Number Differences
Keep the task down to one number in your head at a time:
- When a digit appears, take the smaller of the pair from the larger and type the gap straight away.
- Then let go of the old digit and hold only the new one. You never need anything older.
- Say the held digit silently while you type, so it survives the keypress.
- Candidates report gaps of 1 to 4 only, so a gap you work out as 5 or more means you have lost or misread a digit.
- If you lose track, let one digit pass, hold it, and start again from the next pair. One miss costs less than a run of guesses.
Worked example
The digits arrive as 4, 8, 5, 6, 2. Nothing is due for the first digit. For 8, type 4 (8 minus 4). For 5, type 3 (8 minus 5). For 6, type 1 (6 minus 5). For 2, type 4 (6 minus 2). The answers are 4, 3, 1 and 4.
Each answer uses only the last two digits. By the time 2 appears, the 4, 8 and 5 no longer matter.
Tips for the real Number Differences test
- Use the practice round, which candidates report you can repeat, to settle into the pace before the scored rounds.
- Rest your hand on the number pad before the first digit and keep your eyes on the screen. Looking down can cost you the next digit.
- Practise without pauses between digits. Candidates say prep software that paces you between digits made the real rounds feel faster.
- Expect the later rounds to feel long. Keep the same method in round eight as in round one.
- Do not type before you have read the new digit. An answer typed ahead is a guess.
Practise Number Differences on CogniPrep
Our Number Differences game runs 8 timed rounds of 2 minutes, with each digit on screen for 2 seconds and every gap between 1 and 4. Your answer brings the next digit, with no feedback until the end and no practice round first. Your score out of 100 is based on correct answers per minute, less a third of a mark for each wrong answer, so random keypresses gain nothing. That rule is ours, because the FAA does not publish how the section is scored. On a phone you tap an on-screen keypad, which is slower than the real number pad.