Grade 4 · Unit 2: Fractions and decimals

Calculating with decimals

Add, subtract, multiply, divide and round decimals.

Fuel pumps show decimals for the amount and the price.

Decimals every day

Fuel pumps, scales and shop bills use decimals. We need to add, subtract, multiply and divide them. Always estimate first.

Adding and subtracting

Line up the decimal points, then add as normal. Fill empty places with zeros: 8.6 = 8.60. 15.2 − 7.85 = 7.35 (write 15.20 first).

Multiplying decimals

0.4 × 3: 4 × 3 = 12. One decimal place → 1.2. 1.5 × 0.2: 15 × 2 = 30. Two decimal places → 0.30 = 0.3. Check with an estimate: 1.5 × 0.2 is a bit less than 2 × 0.2 = 0.4.

Dividing decimals

4.8 ÷ 4 = 1.2: share 48 tenths into 4 groups of 12 tenths. × 10 moves digits one place left; ÷ 100 moves them two places right: 37.5 ÷ 100 = 0.375. 6 ÷ 0.5 = 12: how many halves in 6?

Rounding decimals

To round to a whole number, look at the tenths: 3.46 → 3. To one decimal place, look at the hundredths: 3.46 → 3.5. A shirt at ৳749.50 is about ৳750.

What I learnt