Hi Oleg

Yes, it would be relatively easy to divide 11730 by 10 and look at 1173, but my reason for treating the problem as I did is this:

When competing in the Mental Calculations World Championships, the prime factors problems have to be solved with the prime factors themselves given in ascending numerical order. If I had originally divided by 10 and then checked for the factors of 1173, the factor of 3 would have appeared out of order. However, if a brief check had revealed no factors of 3 in the number, then it would be better to divide by 10 to begin with - and, of course, to record one factor each of 2 and 5.

Best regards,

George Lane

Oleg Stepanov <

olegstepanov@...> wrote:

GL> Sample problem: Find the prime factors of 11730

GL> 11730/2=5865, which is not divisible by 2

GL> 5865/3=1955 which is not divisible by 3

GL> 1955/5=391 which is not divisible by 5, 7, 11 or 13

GL> 391/17=23 which is a prime number

GL> The list of prime factors is thus 2, 3, 5, 17, and 23.

Please, I fill myself little strange. Probably I do not understand

something. Why not divide on 10 and by looks full number 11730 think

only about 1173? Your method remind me Jededia Buxton what by multiple

on 300 made it by 5, 20 and 3.

Apologize if I am not correct or did not find explanation...

Sincerely Yours Oleg Stepanov.

http://www.lk.net/~stepanov/
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