KS2 SATs Maths: Decimals and Percentages Revision Guide

Decimal place value

The first digit after the decimal point is tenths, the second is hundredths, the third is thousandths. 0.35 means 3 tenths and 5 hundredths.

Converting fractions to decimals

Fractions with a denominator of 10, 100 or 1000 convert directly: 3/10 = 0.3, 7/100 = 0.07. For other fractions, divide the numerator by the denominator.

Percentages

Per cent means "out of 100". 50% = 0.5 = 1/2. To find a percentage of an amount, find 1% (divide by 100) then multiply by the percentage you need, or use known facts like 10% is dividing by 10.

Comparing and ordering

To compare fractions, decimals and percentages together, convert them all to the same form (usually decimals or percentages) before ordering.

Common mistakes

• Misaligning decimal points when adding or subtracting decimals.
• Forgetting that a longer decimal isn't always bigger — 0.4 is bigger than 0.25.
• Mixing up "increase by 10%" with "find 10%".