Arithmetic (all content)
- Multiplication as equal groups
- Intro to multiplication
- Basic multiplication
- Multiplication with arrays
- Understand multiplication using groups of objects
- Multiply with arrays
- Worked example: Whole numbers on the number line
- Represent multiplication on the number line
- More ways to multiply
- Ways to represent multiplication
Sal uses arrays and repeated addition to visualize multiplication. Created by Sal Khan.
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- can you multiply fractions?(17 votes)
- Yes you can! Just multiply the tops of both of the fractions then the bottoms, then simplify. Hope that helps!(16 votes)
- How to do you multiply hundreds and thousands?
For example 100x2000?(14 votes)
- Multiply the numbers without the zeros at the end, then place the total number of zeros at the end of the result.
In your example, do 1x2=2, then place a total of 2+3=5 zeros at the end. So 100x2000 = 200,000.(33 votes)
- who first used multiplication and in which country?(6 votes)
- The oldest known multiplication tables were used by the Babylonians about Iraq 4000 years ago . But he early Egyptians were the first to discover multiplication and to use it effectively as well as teach it to one another.
The modern method of multiplication based on the Hindu–Arabic numeral system was first described by Brahmagupta (598 - died after 665) was an Indian mathematician and astronomer.
Brahmagupta gave rules for addition, subtraction, multiplication and division.(15 votes)
- Is it possible to multiply with powers?(7 votes)
- Yes, you just multiply the numbers, and then add the exponents.
(go down to Multiplying Variables with Exponents)(6 votes)
- can you multiply a decimal?(4 votes)
As we know when you multiply, you would line up the numbers like this:
Now if you wanted to multiply a decimal, it would look like this:
See? You pretty much do the same thing! However, you may stumble across the the problem where you do not know where to put the decimal. You would move the decimal to where the place value of the numbers multiplied. For example, if you did 10.001 * 3 it would be 30.003. The decimal is in the thousandths place on the first number so the answer would have it go to the thousandths place.
But remember, there is an exception to this rule. If you did 10. 05 * 2 it would be 20.1. This may be confusing, because that is in the tenths place instead of the hundredths.
This is because 10.05 * 2 really is 20.10 but you would round off the zero because it is not needed.
This all may be confusing to grasp at first, but as you get better at math, this will make more and more sense. If you need more help, either reply or ask an adult.(4 votes)
- Why do two negatives make a positive? (When multiplied...)(1 vote)
- its sort of how it is, those are the "rules" i mean think about it, its like magnets, when the same sides are put together, they repel and cancel each other out. So 2 negatives would equal a positive. For example, -2 * -2 = 4, -9 * -3 = 27, and so on(2 votes)
I have these three star patches, I guess you could call them, right over here. And so I could say, if I had one group of three star patches, how many star patches do I have? So I literally have one group of three star patches. Well, that means that I have three star patches. 1, 2, 3. This is my one group of three. Now let's make it a little bit more interesting. Let's say that I had two groups. Let's say that I had two groups of three. So that's one group, and then here's a second group. Here's two groups of three. So how many total star patches do I have now? Well, I have two groups of three. Or another way of thinking about it is this is 3 plus 3. This is equal to 3 plus 3, which is equal to 6. So we see 1 times 3-- one group of 3 is 3. Two groups of 3, which is literally two 3's, is 6. Let's make it even more interesting. Let's have three groups of 3. Now, what is this going to be equal to? Well, it's three groups of 3. So I could write this as three groups, 3 times 3. And how many of these star patches do I now have? Well, this is going to be 3 plus 3 plus 3. It's going to be 3 plus 3 plus 3. Notice I have three 3's. I have two 3's. I have one 3. So this is 3 plus 3 plus 3 is equal to 9. And you can count them. 1, 2, 3, 4, 5, 6, 7, 8, 9, or you could just count by 3's. 3, 6, 9. And I think you see where this is going. Let's keep incrementing it. Let's get four groups of 3. So let's think about what 4 times 3 is. 1, 2, 3, and 4. This right over here is four groups of 3. We could write this down as 4 times 3, which is the same thing as 3 plus 3 plus 3 plus 3. Notice I have four 3's. One 3, two 3's, three 3's, four 3's. One 3, two 3's, three 3's, four 3's. So we get 3, 6, 9, 12. So what I encourage you to do now, now that the video is almost over, is to keep going. I want you to figure out what 5 times 3 is, and 6 times 3, and 7 times 3, and 8 times 3, and 9 times 3, and 10 times 3. And I'll give you a little hint. You don't always have to draw the star patches, but it's nice to visualize it. We saw 4 times 3 is literally four 3's. Well, 5 times 3 is going to be five 3's. So 2, 3, 4, 5. Which is equal to 3, 6, 9, 12, 15. So I encourage you to think about what all of these are after this video is done.