Learn to multiply a 3-digit number by a 1-digit number without regrouping. In this video, we will multiply 4x201. Created by Sal Khan.
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- 201x4... easy! 1.Just multiply 200x4 2. Then multiply 4x1 3. Last add the products 800+4=804
I hope this helps(7 votes)
is it always just me or are the videos easy but the test are really hard.
see you next time!(5 votes)
My question is pretty random, but can you ÷ using the same standered way we're using?
I know it works for addition, subtration and multiplacation!
Please answer!! :D
- i got little bit confuse so i watch 3 time then i told my mom to give me answer is that ok(3 votes)
- Has anyone ever heard of lattice multipliation?(2 votes)
- Would the method of adding each number a certain amount of times work as accurately? (E.g, 3 x 123 = 123 + 123 + 123) Thanks in advance!(1 vote)
- The method would work if you were able to add perfectly, making no mistakes - but humans make mistakes all the time. Adding 123 three times is something many people can do without making errors, but one day you will need to multiply 123 by 17.25, and adding a number a lot of times is a lot more time consuming and likely to lead to errors. Computers are good at doing things perfectly, so old computers were often designed to add many times rather than multiply.(2 votes)
Let's multiply 4 times 2,012. Actually, let's make it a little bit simpler. Let's multiply 4 times 201 just to simplify things a little bit. So 4 times 201. So as we've seen in previous videos, I like to write the larger number on top. This is just one of many ways of tackling a calculation like this. I'll write the 201. And then I'll write the 4 right below it, and I'll write it right below the ones place. And so I have 201 times 4. Now, just like we did when we were multiplying a one digit times a two digit, we do essentially the same process. We first multiply 4 times the 1. Well, 4 times 1 we know is equal to 4. So we put a 4 right over there in the ones place. Then we can multiply our 4 times the digit that we have in the tens place. In this case, we have a 0 in the tens place. So 4 times 0, well, that's just 0. 4 times 0 is 0. We put the 0 in the tens place right over here. And then last, we have 4 times this 2 right over here. And so 4 times 2 is equal to 8. And we put the 8 right over here. And we get our answer-- 804. Now, why did this work? Well, remember, when we multiplied 4 times 1, that was literally just 4. And we've got that 4 right over here. When we multiply 4 times 0, that's 0 tens. So we've got 0 tens right over here. And when we multiplied 4 times 2, this was actually a 200. It's in the hundreds place. So 4 times 200 is 800. So what we're essentially doing by writing it in the right place is we're saying, 4 times 201, that's the same thing as 4 times 200, which is 800, plus 4 times 0 tens, which is 0 tens, plus 4 times 1, which is 4. So 800 plus 0 plus 4 is 804.