Video: KS2-M16 • Paper 1 • Question 23

71× 46 = _.


Video Transcript

71 multiplied by 46 equals what?

The way this calculation has been written gives us a very big clue how to work out the answer. We can use long multiplication. To begin with, we’re going to multiply everything by six. One multiplied by six equals six. Now let’s multiply 70 by six. We know that seven times six is 42. So seven tens times six is 42 tens. This is the same as 420. And so 71 multiplied by six equals 426.

Now we need to multiply the digits in 71 by the four digit. Remember, this four isn’t worth for ones. It’s in the tens place. So the first thing we should do is write a zero in the ones place so that everything shifts to the left and becomes 10 times greater. One multiplied by four equals four. So we know that one multiplied by four tens will equal four tens. And because we’ve already put the zero in the ones place, it reminded us to put the four in the tens place. Seven multiplied by four equals 28.

We know because we’ve shifted everything along, what we’ve really worked out is seven tens multiplied by four tens gives us an answer of 2800. But we’ve used the fact seven times four is 28 to help us.

Now we need to add the answers to both multiplications together to find the overall total. Six ones plus zero ones equals six ones. Two tens plus four tens equals six tens. Four hundreds plus eight hundreds equals 12 hundreds. So we can write a two in the hundreds column and exchange 10 of those hundreds for 1000. And then finally, in the thousands column, we have two thousands plus the one that we’ve just exchanged, equals three thousands, 3266.

How do we find the answer? The way the calculation was written gave us a clue to use long multiplication. First, we multiplied 71 by six. Then we multiplied 71 by 40, making sure that the digit shifted along to show that we are multiplying by four tens. Then we added these two totals together to find out what 71 multiplied by 46 is. 71 multiplied by 46 equals 3266.

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