Multiplying Decimals

Steps

1. Ignore the decimal points and multiply as whole numbers
2. Count the total decimal places in both factors
3. Place the decimal point in the product (same total number of decimal places)

Example

$2.4 \times 1.3$

1. Multiply: $24 \times 13 = 312$
2. Count decimal places: $2.4$ has 1, $1.3$ has 1 → total = 2
3. Place decimal: $3.12$

So $2.4 \times 1.3 = 3.12$ ✅

More Examples

$0.6 \times 0.7$:

• $6 \times 7 = 42$
• 2 decimal places → $0.42$ ✅

$3.25 \times 4.1$:

• $325 \times 41 = 13,325$
• 3 decimal places → $13.325$ ✅

Multiplying by 10, 100, 1000

• Multiply by 10: move decimal right 1 place ($3.45 \times 10 = 34.5$)
• Multiply by 100: move decimal right 2 places ($3.45 \times 100 = 345$)
• Multiply by 1000: move decimal right 3 places ($3.45 \times 1000 = 3450$)

Estimation

$4.8 \times 3.2 \approx 5 \times 3 = 15$ Actual answer: $15.36$ ✓ (close!)

Quick check: If both factors are less than 1, the product is less than either factor: $0.3 \times 0.5 = 0.15$