Question Video: Multiplying 2-Digit Numbers by 1-Digit Numbers with Base 10 Blocks Mathematics • 4th Grade

Video Transcript

Find the product 43 multiplied by two by multiplying the tens followed by the ones and then adding. 43 multiplied by two equals what?

In this question, we need to find the product, which is what we get when we multiply two numbers together, of 43 and two. And perhaps you know your two times table up to 10 times two, maybe even 12 times two. But what about 43 times two? This is quite a large two-digit number that we’re dealing with here. How can we multiply this two-digit number by two? Well, the question tells us. First, we’re to multiply the tens, then by the ones, and then add. What does this mean? Well, underneath the calculation, we can see a picture that can help us here. It’s the number 43 modeled out of place-value blocks. And place-value blocks are really useful because they help us see numbers in their different parts. 43 can be partitioned or split up into four tens or 40 and three ones, which of course have a value of three.

Now what this question is telling us to do is not to look at 43 all in one go, but to first think about the tens and multiply 40 by two, then think about the ones and multiply three by two. Now, we know that four times two is eight, and so four tens multiplied by two is worth eight tens or 80. So if we multiply the tens part of our number by two, we get the answer 80. Now let’s multiply the ones; three times two equals six. So we’ve got the answers 80 and six. And to find the overall answer, we just need to combine these two parts back together again. 80 plus six equals 86. We found the product of 43 and two by multiplying the tens, then the ones, and then adding the two answers together. 43 multiplied by two equals 86.