Subtract 5/8 - 2/5 = ? America vs China tricks

 

How to subtract the fraction below in a simple way using both the America way and the Chinese way..

5   - 2

8     5

American Way

5   - 2

8     5

Finding the LCM, that will be 40;

5   - 2  or 5/8  -  2/5

8     5

25 - 16   or 25/40  -   16/40

40   40

    9  or 9/40

   40

Chinese Way

5   - 2

8     5

Multiply diagonally; that is 5 x 5 = 25 and 8 x 2 = 15 ; LCM will be 40 ; that is 

8 x 5 = 40

25 - 16     =  9

40   40        40

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