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Lesson 3: Multiplication as groups of objects

Multiplication as equal groups

Sal uses arrays and repeated addition to visualize multiplication.  Created by Sal Khan.

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• how do you multiply mills and thousands
• you can try converting the number so you only have to multiply the numbers with value example
12000*600 is the same as 1200000*6 then multiply what i'm trying to write is put the zeros behind the larger numbers but don't put numbers with value like 123456789......
• How to do you multiply hundreds and thousands?

For example 100x2000?
• 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.
• can you multiply fractions?
• Yes you can! Just multiply the tops of both of the fractions then the bottoms, then simplify. Hope that helps!
• I do know all my tables by heart but how do stick on to them
• Skip counting also helps. For example, I know 8x8=64 but if I forget how much 7x8 is, all I have to do is subtract 1 eight from 64.

Think about it: 8x8 is the same as 8 eights, so 7x8 is 7 eights. Therefore, 7x8 has 1 less eight than 8x8. So 7x8 is the same as 8x8 - 8, or 64 - 8. Which is 56.
• Can you divide a negative number with a positive number?
• Yes you can your answer will always be a negative number.
• who first used multiplication and in which country?
• 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.
• hello everyone, can someone answer my question please, if multiplication is a repetition of addition , then how to explain 10 X 0.5? using a repetition concept
• (0.5 + 0.5 + 0.5 + 0.5 + 0.5 + 0.5 + 0.5 + 0.5 + 0.5 + 0.5) = (10 X 0.5)
But what about 0.5 x 0.5 using repetition? Well you'd have to jump through some hoops, like change the first decimal to a fraction, say 5/10 (doesn't matter what as long as it equals 0.5), which would allow you to re-write the equation as:
5/10 X 0.5 = (0.5 + 0.5 + 0.5 + 0.5 + 0.5)/10 = 2.5/10 = 0.25
Probably not helpful to think about multiplying decimals as repetition of addition. So I would say it's only useful when multiplying whole numbers.
• haw do i get to fourth grade?
(1 vote)
• Is it possible to multiply with powers?