Video: KS2-M17 • Paper 1 • Question 10

167 × 5 = _.


Video Transcript

167 multiplied by four equals what?

The number 167 is a lot larger than some of the numbers we’re used to dealing with with the four times table. But we can still use the same skills that we use with the four times table and the same number facts to help us to calculate this larger answer.

There’re perhaps two ways to find the answer. The first method we could use is a mental method. Our knowledge of the four times table tells us that when we multiply a number by four, it’s exactly the same as multiplying by two and then multiplying by two again.

In other words, we double and then we double. We can calculate this double-double method using our heads. So let’s do that. To help us double quickly, we could partition the number 167 into 160 and seven because these are two numbers we could double fairly quickly.

Seven doubled is 14 and 160 is the same as 16 tens. 16 doubled is 32. So the answer is 32 tens or 320. 320 plus 14 equals 334. So 167 doubled equals 334. And we need to double again to find the answer to our problem.

Doubling 334 is a little bit more straightforward because we can just double each digit. 334 doubled equals 668. And so by doubling and doubling again, we’ve used our knowledge of the four times table to help us find the answer.

If we would rather use pencil and paper than to double and double in our heads, we could use short multiplication because we’re multiplying by a single digit. To do this, we start by writing the calculation vertically, making sure that the digits are in the correct columns.

First, we multiply the ones by four. What is seven times four? Well, seven fours are 28. So we can write the eight in the ones column. We can’t put another digit in the ones column. And the two stands for two tens. So we’ll put that underneath the tens column.

Now, let’s look at the tens column. What is six tens multiplied by four or 60 multiplied by four? Well, we know that six multiplied by four is 24. So six tens multiplied by four is 24 tens. Don’t forget the two tens that are already underneath. So that’s 26 tens. 26 tens is the same as 260. So we’ll write the 200 in the hundreds column underneath.

Finally, let’s multiply the hundreds. 100 multiplied by four equals 400. And there are 200 underneath. So instead of 400, we have 600. The answer is the same as when we used the doubling method: 668.

So whether we double doubled in our heads or used short multiplication as a written method, we got the same answer. 167 multiplied by four equals 668.

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