How to do multiplication?

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mwestwood's profile pic

mwestwood | College Teacher | (Level 3) Distinguished Educator

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Multiplication requires memorization, but there are some multiplication tables that can be learned because of certain patterns. For example, multiples of 5 end in either 5 or 0 that alternate. 

5x1= 5

5x2 =10

5x3=15

5x4=20

So, one can easily count with this pattern as it moves from 5 to 0 to 5 to 0 and one simply count from 1 to 9 before the zero. Thus, 5,10,15,20,25,30,35,40.45,50,55,60, and so on.

Similarly 2 x numbers is easy if the student just learns the tables 1x2-2; 2x2=4; 2x3=6 [just add 2 each time-(2.4.6.8.10.12,14,16,18,20.....)

Multiples of 9 also follow a pattern that is easily learned because all the student has to do is count 1,2,3, etc. and add what number with that will equal 9. Then, the student has the multiplication table for 9s.

9x1=9   (0+9=9)
9x2=18 (1+8=9)
9x3=27 (2+7=9)  
9x4=36 (3+6=9)
9x5=45 (4+5=9)
9x6=54 (5+4=9)
9x7=63 (6+3=9)
9x8=72 (7+2=9)
9x9=81 (8+1=9)
9x10=90(9+0=9)

Of course 10 times any number is that number plus 0. For example, 4x0=40; 10x10=100, 500x10=5,000 2,000=20,000 and so on.

If a student can find patterns, memorization is much easier.

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lemjay | High School Teacher | (Level 3) Senior Educator

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Take note that multiplication is a shorthand for repeated addition.

For example, if we multiply 10 by 3,

`10 xx 3`

this is the same as adding the 10 by itself three times.

`=10+10+10`

`=30`

Therefore, `10xx3=30` .

degeneratecircle's profile pic

degeneratecircle | High School Teacher | (Level 2) Associate Educator

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Rote memorization will get the job done, but having some sort of number sense, which is hard to define, shouldn't be underestimated. For example, I majored in math, have been teaching math for several years, and I often can't immediately remember parts of the multiplication table. In particular, ` 6 times 7, ` `6 times 8,` and `7times8 ` still aren't burned into my memory. But that's no problem; I know that `3 times7=21, ` so `6times7=42`, twice as much. Similarly, I do have `8times8=64` burned into my brain (not quite literally, thankfully), so `7times8 ` is just 8 less.

Other techniques include multiplying by 10 and then halving in order to multiply by 5: an example not on any multiplication table, `72times5=(72times10)/2=720/2=360. ` I recommend trying to see the answers in as many ways as possible. This builds number sense and reinforces connections to other parts of the multiplication table and mathematical concepts in general.

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Wiggin42 | Student, Undergraduate | (Level 2) Valedictorian

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In all honesty, the best way to learn multiplication facts is to make flashcards and drill. Patterns are useful for visualizing and understanding but rote memorization makes recall times faster. During test day you don't have to time to write it all out or think about your patterns. Quizlet can help you make online flashcards. Khan Academy has drill practice. I prefer physical note cards. Just the act of making flash cards helps you remember as well. Good luck!

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malkaam | Student, Undergraduate | (Level 1) Valedictorian

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Multiplication is how many times a number is added with itself. Easiest way to do multiplication is memorizing the times table, so of them have shortcuts to memorizing them like in table for 2 all even numbers are included, in the table for 5 all numbers end with either 0 or 5, in the table for 9, numbers until 10 are shown below, notice that after being multiplied 5 the numbers are repeating just that their order is different and they are going the opposite way, 45 became 54, 36 became 63 and so on.

9*1=9

9*2=18

9*3=27

9*4=36

9*5=45

9*6=54

9*7=63

9*8=72

9*9=81

9*10=90

In the table for 10 all numbers end in the number 0. Also remember that either it's 10*12 or 12*10 the answer will be same. 

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jess1999 | Student, Grade 9 | (Level 1) Valedictorian

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The best way to learn multiplication is memorizing the times table, it's hard but it definitely helps a lot. Anyways, multiplication basically works like this 

5 × 5 will basically be 5 + 5 + 5 + 5 +5 so adding 5 five times which will give you 25 

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crystaltu001 | Student, Grade 10 | (Level 1) Valedictorian

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Multiplication is when the same number is added multiple times

For example 5*4

Which is equal to 5 + 5 + 5 + 5 

And that's 20

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ayl0124 | Student, Grade 12 | (Level 1) Valedictorian

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One method I use when I must multiply large numbers is factoring.

For example, you need to find out: `48 xx 12` .

Split both numbers into the hundreds, tens, and ones place.

48 would be 40 and 8.

12 would be 10 and 2.

`(40 + 8)(10 + 2)`

Multiply the 40 with the 10 and the 2, and multiply the 8 with the 10 and 2 as well. By doing this, you break up large numbers into smaller ones. Lastly, add all the products together.

`(40xx10) + (40xx2) + (8xx10) + (8xx2)`

And thus...

`(400) + (80) + (80) + (16) = 576` 

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Jyotsana | Student, Grade 10 | (Level 1) Valedictorian

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Multiplication is all about memorizing. You have to take all your time to learn the pattern. For example, 1*3=3, 2*3=6, 3*3=9 4*3=12

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