Long multiplication - KS2 Maths - Learning with BBC Bitesize

What is long multiplication?

Knowing your multiplication facts is very useful, but what happens when the numbers you are multiplying are greater than those in your multiplication tables?

You will need to calculate using a column method, which is another name for long multiplication. This will allow you to multiply up to 4-digit numbers by 2-digit numbers.

You can break the calculation down into parts that are easier to figure out and then add the parts together to get your answer.

Activity: Multiplying larger numbers by two-digit numbers

Complete this interactive activity to better understand multiplying with larger numbers. Then put your knowledge to the test.

Written method for multiplication

Using your times tables knowledge for small single-digit multiplication equations is great.

When you are asked to multiply any two, three or four-digit number by multiples of ten, or any two-digit numbers, then you need a written method.

A column method is the most efficient method to use.

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Start by multiplying the top number by the ones (4). 4 × 1 = 4. Place 4 in the ones column.
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4 × 2 = 8. Place 8 in the tens column.
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4 × 5 = 20. You can put 0 in the hundreds column and carry 2 over.
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4 × 1 = 4. Now add the 2 you carried over 4 + 2 = 6. So 1521 × 4 = 6084.
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Now you need to multiply the number by the tens (20). First you multiply by 10 and then by 2. Placing the zero in the ones column is the multiplying by 10 bit!
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2 × 1 = 2. You can put 2 in the tens column.
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2 × 2 = 4. The 4 goes in the hundreds column.
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2 × 5 = 10. You can put 0 in the thousands column and 1 is carried over to the ten thousands column.
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2 × 1 = 2. Add the 1 you carried over 2 + 1 = 3. So 1521× 20 = 30420.
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Now add the two answers together to get your final answer. 6084 + 30420 = 36504.