Grade 5 · Unit 2: Fractions, decimals and percentages

Decimals

Thousandths, rounding and calculating.

Sprint races are timed to thousandths of a second.

Race times

A sprinter runs 100 m in 10.375 seconds. Times are measured to thousandths. Decimals help us be precise.

Place value

3 tenths, 7 hundredths, 5 thousandths. Three decimal places. 0.375 = 375/1000 = 3/8.

Rounding

To round to 1 decimal place, look at the hundredths: 7 → round up to 10.4. To 2 decimal places, look at the thousandths: 5 → round up to 10.38. To the nearest whole: 10.

Multiplying decimals

1.25 × 4: 125 × 4 = 500. There are 2 decimal places, so 5.00. 0.3 × 0.2: 3 × 2 = 6. 2 decimal places → 0.06. Estimate to check where the point goes.

What I learnt