How To Multiply Integers
In the double digit multiplication 5 represents five units while 4
Hi, my name is Charles and I am one of the Math teachers from Maxim Workshop. I am just going to now teach you how to do some maths. Hi. I am going to show you how to multiply integers together. The basic method of learning how to multiply integers together would come pretty much around key stage 2 when you are doing times tables and possibly key stage 1 if you have got bright learners. The first thing we want to do is to establish just the basic operation. So, we have seven times five. Now, the thing to think about when you're multiplying integers is to possibly think about a scenario that might help you with picturing what seven times five actually looks like. Now, I often try to remember rows and columns. So if we have seven rows and we have seven columns, so it might be in a cinema house where you've got seats arranged. You might want to picture an abacus also. And that might be with seven different color beads, and with each color bead you have five of them. So, I mean that is just the way to picture what seven times five looks like. Now to actually multiply it has to be more direct. So, you come to understand doing stuff like that just by memory and just by rote work. What you would do is seven times five, and that is pretty much equal to thirty five. This does get a little bit more technical when you are doing double digits by single digit numbers. Imagine if we then started going to the value of ten times eight. What I would do here is first of all rearrange this into columns here. And then we start off by multiplying eight times zero, which is zero. And then eight times one, which is eight. And that provides us with an answer of eighty. Now, just as with seven times five, you can see that you are still multiplying single digits by single digits. We are never really multiplying a number like eight by ten directly. But as you get more used to doing numbers like this, then you might instantly be able to notice that eight times ten equals eighty without actually doing the individual operations. Now, another example that I'd show you is when you're doing double digits by double digits. So, we'll go to 72 times 45. So the first thing to do again is to multiply 5 by 2 and then 5 by 7. So we arrive at these two being ten. So we carried a 1. We do 5 times 7 now, which again we've done before and that is 35. Add the one, not to forget, and that is 36. So, we've got 360 from 5 times 72. Now we move to the upper column. Now, you have to notice the difference between this number and this number not because this is just merely higher than the four in terms of one, but this has a power of four times ten. This four represents forty. This five represents five units. For this, we have to shift across one column. Write a zero underneath this zero and start working out 4 times 72, inserting answers from this column onwards. So, 4 times 2 gives us 8 and with nothing to carry on. 4 times 7 is going to be 28. We're going to place the eight here, and then put the two here. Now, we want to add up what we have in these columns. So, zero and zero, that gives us zero. Six and eight gives us fourteen. So we can put the four there, carry the one here. One plus three, that is four, plus eight that is twelve. We put the two there and carry the one. One plus two, that's three. And we've got 3,240. So, 72 times 45 is 3,240. And that's how to multiply integers. .