Grade 4 · Unit 1: Number and place value

Written subtraction

Column subtraction with exchanging.

Saving for a bicycle

A bicycle costs ৳12 500. Tania has saved ৳7 865. How much more does she need? Estimate: 12 500 − 8000 ≈ 4500.

Column subtraction

Ones: 0 − 5. Exchange across the zero: 10 − 5 = 5. Tens: 9 − 6 = 3. Hundreds: 4 − 8? Exchange: 14 − 8 = 6. Thousands: 11 − 7 = 4. Tania needs ৳4635 more.

Zeros

Exchanging across many zeros is tricky. Think: 6000 = 5 thousands, 9 hundreds, 9 tens and 10 ones. Or count up: 2748 → 3000 → 6000: 252 + 3000 = 3252.

Check with addition

Add the answer to the number you subtracted. You get back to 12 500. The answer is correct!

Five-digit numbers

The column method works for 5-digit numbers too. Choose: mental method for easy numbers, written method for hard ones. Check: 26 555 + 18 675 = 45 230 ✓

What I learnt

• I can subtract 4- and 5-digit numbers in columns.
• I can exchange across zeros.
• I can check by adding.