Decimal Places (d.p.)

Count the digits AFTER the decimal point. Look at the next digit to decide whether to round up.

Example: 3.1415 to 2 d.p. → 3.14 (the next digit 1 is less than 5).

Rounding Up

If the next digit is 5, 6, 7, 8, or 9, add 1 to your target digit.

Example: 7.86 to 1 d.p. → 7.9

Nearest Unit

Rounding to the nearest whole number, ten, hundred, etc.

Example: 382 to nearest 10 → 380 382 to nearest 100 → 400

Large Numbers

When rounding to nearest 10/100, replace the dropped digits with zeros to keep the size correct!

Significant Figures (s.f.)

The first significant figure is the first NON-ZERO digit from the left. Zeros at the start don't count!

Example: 0.00456 to 2 s.f. → 0.0046

Zero as Significant

Once you start counting s.f., all zeros AFTER that are significant.

Example: 5.03 is 3 s.f. Zeros in the middle or at the end count if they follow a non-zero digit.

Scientific Notation Link

Significant figures are related to Standard Form. 3.4 × 10⁵ is 2 s.f.

Estimation Consistency

Always round to 1 s.f. when estimating a calculation result.