Forecast and projection questions

Numerical reasoning practice > Forecast and projection questions

A forecast question asks you to continue a trend. The whole question turns on one distinction: growing at the same rate is not the same as growing by the same amount.

1. Rate versus amount

If revenue goes from 1,600 to 2,080, that is:

• An increase of 480 (an amount)
• An increase of 30% (a rate)

Continuing by the amount gives 2,080 + 480 = 2,560. Continuing at the rate gives 2,080 × 1.3 = 2,704. Both are reasonable-looking numbers and both will be among the options.

The question will say which. "At the same percentage rate" means multiply. "By the same amount" means add.

2. Worked example: continuing a growth rate

The table below shows the revenue of each product.

Product D 500 → 650
Product C 1,600 → 2,080
Product B 500 → 600
Product A 1,900 → 2,660
(2022 and 2023, unit: £000s)

If Product C grows from 2023 to 2024 at the same percentage rate as from 2022 to 2023, what will its revenue be in 2024?

How to work it

• Find the rate from the two years given: (2,080 − 1,600) ÷ 1,600 = 480 ÷ 1,600 = 30%
• Apply it to the later year, not the earlier one: 2,080 × 1.30
• 2,080 + 624 = 2,704 (£000s)

Applying the rate to 1,600 instead of 2,080 is the single most common error here, and it produces 2,080 — which is already on the page, so it looks right.

3. Use a multiplier, not two steps

Growing by 30% is one multiplication by 1.3, not "find 30% then add it". One step is faster and gives fewer chances to slip.

• +30% → × 1.3
• −15% → × 0.85
• Two years of +10% → × 1.1 × 1.1 = × 1.21, not +20%

That last line is compounding, and it is worth knowing because a two-year projection at a constant rate is a common question.

4. What a forecast question assumes

These questions are arithmetic, not forecasting. They assume the rate continues exactly, which real revenue never does.

That matters for one reason: if a question asks what "can be concluded" from a trend rather than what the projected value is, the answer is usually that nothing can be concluded about periods outside the data. Continuing the line is only valid when the question tells you to.