Division by 5

Often, instead of dividing by 5, it is more convenient to multiply first by 2 and then divide the result by 10. For example,

1375/5 = 2750/10 = 275.

Another examples:

7205/5 = 14410/10 = 1441.

And a third one

980/5 = 1960/10 = 196.

(So multiplication by 2 can speed up division by 5 (and vice versa, of course.) There are simple ways to double natural numbers.)

The latter example suggests another way of dividing by 5: the order of the two tasks "multiply by 2" and "divide by 10" could be reversed if the number ends with 0. In this case, it is as easy to divide by 10 first:

980/5 = 98×2 = 196.


[an error occurred while processing this directive]

|Contact| |Front page| |Contents| |Algebra| |Up|

 

Copyright © 1996-2018 Alexander Bogomolny
[an error occurred while processing this directive]
[an error occurred while processing this directive]