Video instructions and help with filling out and completing Form 2220 Multiply

Instructions and Help about Form 2220 Multiply

Hi welcome to math antics in our last video we learned the basics of multi digit multiplication we learned how to multiply a multi digit number by a one digit number but in this video we're gonna take it to the next level we're gonna learn how to multiply a multi digit number by another multi digit number you remember the procedure for multiplying when we have a one digit bottom number right you break up the problem into a series of multiplication steps one for each of the top digits and in each step you just multiply the bottom digit by a top digit starting with the ones place and working your way left until you've multiplied all of the digits well when the bottom number of your multiplication problem also has more than one digit you have to do that same procedure we learned for each bottom digit for example if you have a two-digit bottom number you multiply the first digit by each top digit and then you multiply the second digit by each top digit that means you're gonna have twice as many steps to do and it means you're gonna get two different answers what how can we have two different answers for the same problem now don't panic the different answers are just what you get from doing the multiplication procedure for each digit of the bottom number separately in fact it's kind of like we're pretending we have two separate multiplication problems that each have a one digit bottom number which is nice cuz I kind of like pretending no Luke I am your father that's impossible Music Laughter well I mean it's nice because we already know how to multiply when we have a one digit bottom number but then what will we do with the two different answers we're gonna get well it turns out that all we have to do is add them together once we're finished doing all of our multiplication steps are you ready to see an example it should make a lot more sense when you see the procedure in action so let's multiply 324 a three-digit number by 46 a two-digit number now remember we're gonna do the same procedure that we did in the last video for each of the bottom digits and since our top number has three digits that means there'll be three multiplication steps for the first digit and three steps for the second digit fortunately we can start the same way we would if the bottom number only had one digit by just ignoring the second digit until we finish the first three steps alright so our first multiplication step is six times four which is 24 and since 24 has two digits we can leave the four in our answer line but we need to carry the two and put it above the next top digit that we're going to multiply so the next step is 6 times 2 which is 12 but we have to add in the 2 that we carried so 12 plus 2 which gives us 14 that's another two-digit answer so we leave the 4 in our answer line and carry the 1 up above the next digit that we're going to multiply and our third step is 6 times 3 which is 18 and then we add in the one that we carry then we get 19 this time we can leave both digits of the 19 and our answer line because there's no more multiplication steps to do well at least there's no more steps for the first digit remember we still have that other bottom digit that we've been ignoring now we have to multiply it by each of the cottage it's also which means we have three more steps to do it also means that we'll get a second answer and because we'll get a second answer we need to start a second answer line for the next set of steps we're gonna put our new answer line just below the first one so this answer line comes from our first bottom digit and this answer line will come from our second bottom digit at the very end after we're all done multiplying we're gonna add the two answers together but for now let's continue with the second set of multiplication steps oh and I almost forgot to tell you there's something very important that you need to do when you start the second set of steps because the second digit of the bottom number is in the tens place that means that even though the digits only a for its value is really 40 that's 10 times bigger so the answer we get should also be 10 times bigger so before we start multiplying we need to put a zero in the first spot of our answer line so it's ten times bigger that means that all the other answer digits we put there are shifted to the next bigger number place and just so you know if we happen to have a third bottom digit we would get a third answer line and we need to shift the third answer over by two zeros because it would be a hundred times bigger and if we had a fourth digit there'd be a fourth answer line shifted over by three zeros and if we had a fifth bottom digit there'd be a fifth answer line shifted over by four zeros see the pattern boy am i glad we've only got two bottom digits and now you see why we always put the number with the fewest digits on the bottom when we're multiplying but let's continue with our problem let's do the first step of our second bottom digit we multiply that digit four by the ones place digit of the top number which is also a four four times four gives us sixteen and that goes in our