I have multiplied all odd integers below 15.
The penultimate digit of the 6digit resulting number is 3.
The above hint is sufficient for restoring the correct result without reverting to my multiplication.
Go ahead, replace the asterisks by digits: N=****3* !
In retrospect I could have done this without the 3 because I know 7*11*13 = 1001 so I just had to do 3*5*9 in my head.
3*5*9 = 135 so 1*3*5*7*9*11*13*15 = 135135
What I
actually did was fill in the 5 at the end. Then the 1001 occurred to me so I wrote _35_35 and figured the missing digits had to match and make the digit sum divisible by 9. So they are both 1's.

Posted by Jer
on 20131008 13:57:09 