Open any finance model and you will find number series. A loan balance that falls, an asset that loses value, a deposit that compounds: each is a row of numbers with a rule. Spotting the rule is the daily work of the job, which is why pattern questions sometimes appear in finance hiring tests.
Arithmetic series: straight-line depreciation
Suppose a company buys equipment for £12,000 and writes it off evenly over four years. The book value at the end of each year runs 12,000, 9,000, 6,000, 3,000, 0. The gap is 3,000 every time.
That is a steady staircase of the simplest kind. Once you see it, you do not need a calculator to say the value after year three: 12,000 − 3 × 3,000 = 3,000.
Geometric series: compound interest
A deposit of £1,000 at 5 per cent a year grows to 1,050, then 1,102.50, then about 1,157.63. Each value is the last one multiplied by 1.05. The ratio is constant, the gap is not: the gaps (50, 52.50, about 55.13) themselves grow.
This is why the two kinds of growth feel so different over time, and why distinguishing them at a glance is a real skill. A row whose gaps are constant adds; a row whose ratios are constant compounds.
Geometric series falling: reducing-balance depreciation
Write an asset off at 20 per cent of its remaining value each year, starting at £10,000, and the book values are 10,000, 8,000, 6,400, 5,120, 4,096. Each is 0.8 times the last.
The gap falls every year (2,000, 1,600, 1,280, 1,024), which is the signature of a ratio rule rather than a step rule. A practised eye reads this from the numbers before reaching for a formula.
Why this matters for tests and for work
Both skills use the same two questions: what are the gaps, and what are the ratios? An analyst who asks them automatically will catch a figure that does not fit the pattern, and that is how many errors in a model get caught: not by recalculating everything, but by noticing that one number breaks the run.
Employers use tests like this as a quick look at comfort with numbers. A widely cited meta-analysis by Schmidt and Hunter compared selection methods across 85 years of research, which is the usual reason cognitive-style tests appear in hiring at all. It speaks to general reasoning tests as a family, not to any one series test, and it is not a claim about the JobCannon test.
Where to practise
The JobCannon Number Series test gives you a scored set that is broken out by kind of rule, so you can see whether steady steps (the arithmetic side of finance) or growing steps and chained rules are your weak spot. It is an in-house test with no published norms, so treat the result as practice feedback.
For the tables, percentages and ratios that dominate real finance papers, the JobCannon Numerical Reasoning test is the better match, and the blog has pieces on numerical reasoning for accounting and investment banking. The number series practice page has extra series to drill.