arnivorous wrote:

Example:

19*18=

1. Take the first number and add it with the units digit of the second number.

19+8=27

2. Multiply the result by 10

27*10=270

3. Multiply the units digit of the first number with that of the second number

9*8=72

4. Add the result of step 2 and 3 together

270+72 = 342

It would be much better to know the multiplication tables of numbers up to 19. Numbers up to 19 are used often and knowing their tables can speed up your calculations considerably

Then 18*19 is straight forward.

18*9 = 162. Write 2 and carry 16

18*1 = 18. Add 16 to get 34. You get 342.

Also, learning tables is not as hard as you might imagine.

e.g. 18*2 we know is 36. 18*3 is 18 more than 36

18*5 = 90 (12*5 = 60, 13*5 = 65, 14*5 = 70 and so on...). 18*4 is 18 less than 90. 18*6 is 18 more than 90

18*10 = 180. 18*9 is 18 less than 180.

All you really need to learn up is 18*7 and 18*8.

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Karishma

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