Written Multiplication
Multiply two-digit and three-digit numbers by a one-digit number using formal written layout
What a learner can do afterwards
- Set out and solve 47 × 6 using short multiplication
- Set out and solve 234 × 5 using short multiplication with carrying
- Check the answer using estimation (e.g. 234 × 5 ≈ 200 × 5 = 1000)
1 · Read
You already know how to set out multiplication in columns. Now you will multiply bigger numbers, where some digits multiply to 10 or more. When that happens, write the ones digit in the answer and carry the tens digit to the next column, just like you do in written addition.
Look at 47 x 6. Multiply the ones first: 7 x 6 = 42. Write the 2 in the ones place and carry the 4 tens above the tens column. Next, multiply the tens: 4 x 6 = 24, then add the carried 4 to get 28. Write 28. The answer is 282.
Now try a three-digit number: 234 x 5. Ones: 4 x 5 = 20, write 0, carry 2. Tens: 3 x 5 = 15, add the carried 2 to get 17, write 7, carry 1. Hundreds: 2 x 5 = 10, add the carried 1 to get 11, write 11. Put it together: 234 x 5 = 1170.
Before you multiply, round the bigger number to check your answer sounds right. For 234 x 5, round 234 to 200: 200 x 5 = 1000. Your exact answer should land near that estimate, not miles away from it.
Carry the extra tens into the next column, and always check your answer with a quick estimate.
More to read
1.4 Multiply Whole Numbers
Multiplication is a fast way to add the same number again and again. When you see 4 x 6, picture 4 groups with 6 things in each group. Counting them one by one is slow, but the multiplication table gives you the total in a flash.
Start with easy facts you already know, like 2s, 5s and 10s. Then build up to harder ones. Every new fact you learn makes the next one quicker, and soon long calculations feel simple.
Multiply by using familiar strategies
Good calculators choose easy paths. Doubling and halving, rounding and adjusting, splitting by place value: each turns hard facts simple. There is rarely one right method.
Compare methods with a friend. Explaining why your path works teaches the maths twice.
2.1: Multiplication of Whole Numbers
To multiply whole numbers, think of equal groups or neat rows. The fact 5 x 3 means 5 rows with 3 in each row, which is 15 altogether. Arrays of dots make this easy to see.
Short practice every day builds speed. Fast recall of small facts leaves your brain free for bigger problems.
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2 · Watch
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Where it sits
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17 questions wait behind this lesson, each with its answer explained. Every answer feeds the sky: stars light as they are learned, and dim when it is time to come back.