Video: KS2-M16 • Paper 3 • Question 19

Circle two numbers that multiply together to equal 1 million. [A] 200 [B] 2,000 [C] 5,000 [D] 50,000


Video Transcript

Circle two numbers that multiply together to equal 1000000: 200, 2000, 5000, 50000.

Before we start thinking about multiplying to make 1000000, what do we know about the number 1000000? How do we write 1000000? 1000000 is a thousand thousands. And so we write the digit one followed by six zeros.

Another way to think of it is 10 lots of 100000. And we can use this particular calculation to help. Which two numbers multiply together to make 10? Well, obviously, one and 10, but also two and five. And so 1000000 is the same as two multiplied by five multiplied by 100000. How can this help us?

Well, we can predict that the two numbers we need to multiply together are going to consist of one of these numbers that has the digit two at the start, together with one of these numbers that has the digit five at the start. What do we multiply two or five by to make each number?

200 is two lots of 100. 2000 is two lots of 1000. 5000 is five lots of 1000. And we multiply five by 10000 to get 50000. We know where we get the two and the five from. But which two numbers can be multiplied together to get 100000?

There are several ways to make 100000. But the one we’re most interested in is 100 multiplied by 1000. So we can say that 1000000 is the same as two multiplied by five multiplied by 100 multiplied by 1000. And we know that we can multiply numbers in any order and it will give us the same answer. So how can we group the numbers two, five, 100, and 1000 to make a calculation that will equal 1000000?

Well, we know that 200 equals two multiplied by 100 and 5000 equals five multiplied by 1000. Another method we could’ve used is to use our knowledge of number facts. We know that multiplying the digits two and five together gives us an answer of 10. This provides us with the one and one of the six zeros we need to make up the number 1000000.

Because of the way that multiplying by multiples of 100 or 1000 works, we know we’re looking for two numbers that have five zeros between them. 200 has two zeros and 5000 has three zeros. And we know that, by multiplying them together, we’re going to get an answer with five zeros. There’s already a zero on the end of the 10. So that gives us six zeros altogether.

Finally, let’s check our two answers are correct. Two multiplied by five equals 10. So two lots of 5000 equals 10000. And so 200 multiplied by 5000 is 100 times more than this. 100 times more than 10000 is 1000000. So the two numbers that multiply together to make 1000000 are 200 and 5000.

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