Learn the 3-Step Method
1Ignore the decimal point.
Treat 3.2 as 32 and multiply: 32 × 4 = 128.
2Count the decimal places.
The question had 1 digit after the point (the .2), so the answer needs 1.
3Put the point back.
128 with 1 decimal place → 12.8.
Worked Example
Work out 2.35 × 3.
Watch Out! Common Mistakes
Wrong! The estimate (about 12) shows this is 10× too big. Answer: 12.8.
Wrong! 2.35 has two decimal places, so the answer needs two: 7.05.
Wrong! The 0.2 must be multiplied too: 0.2 × 4 = 0.8, giving 12.8.
⬇ Cheat Sheet
- Estimate first with whole numbers.
- Multiply ignoring the decimal point.
- Count decimal places in the question.
- Put the same number of places back into the answer.
📖 Continue Your Journey
Quick summary
- Estimate first using whole numbers — it catches place-value slips.
- Multiply as if there were no decimal point: 32 × 4 = 128.
- Count the decimal places in the question and restore them: 12.8.
- 2.35 × 3: 235 × 3 = 705 → two places → 7.05.
Frequently asked questions
How do you multiply a decimal by a whole number?
Ignore the decimal point and multiply the whole numbers, then put the point back so the answer has the same number of decimal places as the question: 3.2 × 4 → 32 × 4 = 128 → 12.8.
Why estimate first?
An estimate like '3.2 × 4 ≈ 12' instantly exposes answers that are 10 times too big or small — the most common decimal multiplication error.
What is 2.35 × 3?
7.05. Multiply 235 × 3 = 705, then restore two decimal places.
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