Aon Digit Challenge: Numerical Reasoning Practice for Technical Applicants

Aon Digit Challenge practice should focus on completing arithmetic equations with distinct digits, then checking every constraint before submitting. Technical applicants may be comfortable with algebra and still lose time by repeating a digit, misreading an operator, or doing more calculation than the equation requires. The useful habit is to work backward from the target, narrow the possibilities, and verify one valid answer.

This article covers the publicly described digitChallenge format and original preparation exercises. It does not establish which employers assign the module or predict your assessment questions.

What Aon confirms about digitChallenge

Official facts: Aon's candidate preparation page lists digitChallenge as a six-minute numeracy test involving mental arithmetic. Its public practice PDF describes filling blanks with digits from 1 through 9, using each digit at most once within an equation. The published tasks use addition, subtraction, and multiplication; more than one answer can be valid. The PDF also describes difficulty responding to correct and incorrect answers.

Those statements describe the provider's public format. Your invitation and introductory screens govern your attempt, including any adjustments. Do not infer a universal pass mark or a required number of completed items from the six-minute description.

Candidate-report boundary: We did not verify two independent, current reports establishing digitChallenge for a particular technical hiring process. Reports about other Aon games do not fill that gap. Preparation inference: The exercises here train the arithmetic and constraint checks in the official format; they are original examples, not candidate-reported assessment items.

Identify the numerical task before practising

An invitation saying “numerical reasoning” is not enough to identify the exact exercise. Aon's public page separately lists digitChallenge, scales numerical, and scales eql. Check the module name rather than assuming every numerical test uses missing digits.

A technical candidate might otherwise prepare chart interpretation when the invitation calls for equation completion. The reverse mistake is equally costly: being fast at multiplication does not prepare you to identify the right denominator in a data table. Aon's assessment-selection guidance explains that employers choose ability-test variants according to what they want to evaluate. A role title alone does not identify the chosen variant.

When reading the introduction, answer three practical questions: What do I enter? Which symbols are fixed? What makes an answer invalid? Separate a deadline for opening the assessment from the clock inside an individual module. Keep your preparation notes tied to the actual task name.

A solving method that protects accuracy

For these original drills, use single digits 1–9, no repeats within a row, fixed printed operators, and ordinary multiplication precedence. Parentheses, where printed, remain fixed. You do not need to use all nine digits. These are explicit practice rules, not a substitute for the instructions shown in your portal.

Read the equation's shape before choosing digits. A subtraction target near nine requires a large first digit. A multiplication-plus-addition target suggests looking for a product just below the target. A multiplication-minus-subtractions target suggests a product above it, with a feasible remainder.

Next, calculate a bound. For two distinct positive digits, the largest sum is 17 and the largest product is 72. Bounds eliminate whole branches: a product of 12 cannot support subtracting positive digits to reach 20. This is faster than trying arbitrary combinations and remembering every failure.

Then work backward. In a × b − c = 29, consider products slightly above 29: 30, 32, and 35. A product of 32 leaves 3, giving 8 × 4 − 3 = 29. Verify that 8, 4, and 3 differ. Stop when you have a valid answer; finding every answer is a different exercise.

Finish with two independent checks: evaluate the expression as printed, then check the digits. A correct numerical result does not excuse a repeated digit. Keeping those checks separate makes it easier to notice the exact mistake under pressure.

Six original practice equations with worked answers

Try each row before reading the explanation. The answers shown are examples; several rows admit other valid assignments.

Original equation	One valid answer	Main check
a − b = 6	8 − 2 = 6	Positive, distinct digits
a + b − c = 12	9 + 7 − 4 = 12	Remainder and uniqueness
a × b + c = 31	7 × 4 + 3 = 31	Multiplication first
a × b − c = 29	8 × 4 − 3 = 29	Product above target
a × b − c − d = 43	7 × 8 − 9 − 4 = 43	Two-digit remainder
a + b × c − d = 35	6 + 4 × 9 − 7 = 35	Four distinct digits

Subtraction: narrow the first digit

For a − b = 6, a must exceed 6. The possibilities begin with 7, 8, and 9, leaving 1, 2, and 3 respectively. Any resulting pair is valid. There is no advantage in checking first digits below seven once you recognize the bound.

Notice what the method preserves: you are selecting a feasible first digit and deriving the second. You are not guessing both independently. The same reduction becomes more valuable as more blanks appear.

Addition and subtraction: derive the remainder

For a + b − c = 12, choose a distinct pair whose sum exceeds 12. With 9 and 7, the sum is 16, so c = 4. All three digits differ. The alternative 8 + 8 − 4 = 12 reaches the target but breaks the nonrepetition rule.

This is a useful diagnostic example. If you repeatedly choose repeated-digit answers, more arithmetic speed is unlikely to fix the underlying error. Train the validity check until it is part of selecting a candidate, not an afterthought.

Multiplication and addition: look below the target

For a × b + c = 31, a product of 28 leaves 3. Choose 7 and 4 for the product. The candidate 5 × 6 + 1 = 31 also works. You only need one admissible solution.

Trying to add first produces a different expression. 7 × (4 + 3) equals 49, not 31. Do not introduce parentheses that are absent from the prompt. Write the intermediate product during slow practice until operator precedence becomes dependable.

Multiplication and subtraction: look above the target

For a × b − c = 29, use 32 and subtract 3. Another route uses 35 and subtracts 6, giving 5 × 7 − 6. A tempting product of 30 leaves 1, which also permits 5 × 6 − 1.

The point is flexibility. Memorizing one displayed answer is less useful than remembering how to look for nearby products. If the first factor pair uses a digit needed for the remainder, try another product instead of forcing an invalid assignment.

Two subtractions: check the available digits

For a × b − c − d = 43, choose 7 × 8 = 56. The remaining subtraction must total 13. Digits 9 and 4 satisfy that total without reusing 7 or 8.

A different attempted pair, 7 and 6, would also total 13 but repeats the multiplier 7. That makes it invalid. A remainder is not solved until you can construct it using the still-available digits. This is where tracking the used set matters more than remembering multiplication facts.

Mixed operators: preserve the expression

For a + b × c − d = 35, use 4 × 9 = 36. You then need a − d = −1; choose 6 and 7. The four digits are distinct, and 6 + 36 − 7 = 35.

The negative intermediate difference is allowed in this practice expression; the selected digits remain positive. Do not confuse a constraint on entered digits with a requirement that every intermediate quantity be positive. Read the actual assessment instructions before transferring any assumption.

Diagnose slow answers instead of chasing a score

Track error types during practice. “Wrong” hides several different problems, each requiring a different correction.

Observation	Likely practice issue	Useful next drill
Result is right, digit repeats	Validity checking	Reject repeated-digit alternatives
Result changes with grouping	Operator precedence	Write the product before adding
Many branches tried	Weak bounds	State possible sums or products first
Valid answer found but search continues	Unnecessary completeness	Stop after one checked solution
Repeated subtraction slips	Arithmetic fluency	Practise complements to nearby products

These diagnoses are preparation inferences, not an interpretation of Aon's proprietary score. Keep a small log with the equation, your answer, elapsed time, and error category. Count valid solutions rather than merely attempted items. Do not turn a home-practice percentage into an asserted employer cutoff.

For example, a session with eight attempted rows and six valid answers tells you where to investigate. If both errors reused digits, repeat the uniqueness drill. If both were multiplication slips, practise the affected facts. The numbers are a hypothetical record, not a recommended pass target.

Use timing after the rules become reliable

Begin with untimed equations and explain the reasoning aloud. Next, solve a short mixed set while recording time, without changing the rules. Only then try a bounded practice session. Keep its duration and conditions explicit so you can compare it fairly with your earlier work.

A short personal time limit can encourage you to notice when you are stuck, but it is not an official per-question allowance. If your assessment offers navigation or skipping, use it according to the displayed instructions. Do not assume the controls of a practice PDF reproduce the live interface.

For a useful retest, preserve the same number of blanks and the same operator pattern while changing the digits and target. Compare valid-answer time only across similarly constructed items. A faster second attempt on an identical equation mostly shows recall. A faster answer on a new equation with the same constraints is better evidence that your method is becoming easier to apply.

Review a difficult item after the session by identifying the first useful bound you missed. That review is more informative than simply repeating the answer. Change the target or operator pattern when creating another drill; otherwise you may be timing memory rather than reasoning.

For accessibility adjustments or a blocked attempt, contact the inviting organization or provider before improvising a workaround. Aon's public preparation guidance addresses adjustments and technical interruptions. Follow the materials and assistance rules in your own introduction; do not assume a calculator is permitted because another numerical module allows one.

Sources and Further Reading

• Aon: public digitChallenge practice tasks and explanations
• Aon: prepare for your online assessment
• Aon Assessment: choosing ability-test variants

Research checked October 1, 2026. Module assignment, assessment conditions, and employer decisions can vary; your invitation remains authoritative.