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Decimals & Rounding

Year 7 🔢 Number Add, subtract decimals, round to decimal places and significant figures.

Decimals represent parts of a whole using place value to the right of the decimal point.

Hundreds	Tens	Ones	.	Tenths	Hundredths	Thousandths
3	4	7	.	2	6	1

So 347.261 = 300 + 40 + 7 + 0.2 + 0.06 + 0.001

Rounding makes numbers simpler while keeping them close to the original value.

Identify the place you are rounding to (e.g. 2 decimal places).
Look at the next digit to the right.
If it is 5 or more, round up. If it is 4 or less, round down (keep the same).

Example: Round 6.374 to 2 d.p. The 3rd decimal digit is 4 (less than 5), so keep the 7. Answer: 6.37

Example: Round 8.158 to 2 d.p. The 3rd decimal digit is 8 (5 or more), so round up. Answer: 8.16

Significant figures (s.f.) measure the precision of a number, counting from the first non-zero digit.

⚡ Key Rule

Start counting s.f. from the first non-zero digit.

Example: 0.004762 to 2 s.f. — First s.f. is 4, second is 7. Next digit is 6 (5 or more), round up. Answer: 0.0048

💡 Trailing zeros after a decimal point are significant: 3.40 has 3 s.f.

🎯 Ready to test yourself? Click the Quiz tab above to answer questions on this topic!

🎬 Interactive Demonstration — Decimals & Rounding

Number: 3.456

Round to (d.p.)

🧮 🔢 Rounding Practice Tool

Number to round

Decimal places

Sig. figures