Maybe it's a series of numbers divisible by 7, i.e 140721 (7 X 20103). But, as for a way to look at a number and determine it's divisible by 7, I don't know of one.
Maybe it's a series of numbers divisible by 7, i.e 140721 (7 X 20103). But, as for a way to look at
Perhap, but she never said what it is seven times, just that it is divisible of seven. So, that suggests she used a fast mental arithmetic test which basically only confirms whether remainder would be zero. :) Such as.. if you add all the digits of a number together (in base 10), and the resulting number is divisible by 3 or by 9, then the original number is divisible 3 or nine respectively. (also then you can repeat it, just keep adding digits of result number until you boil all the way down to single digit hmmhmm!
Any base 10 number divisible by 2, 4, or 8 if the final 1, 2, or 3 digits (respectively) alone are divisible that number. There are kind of easy tricks up to ten for any number, but 7 only I know of is more difficult ones.
Perhap, but she never said what it is seven times, just that it is divisible of seven. So, that sugg
maybe she used this method and was on the toilet for a long time. step zero memorise this repeating sequence 1, 3, 2, 6, 4, 5 Step one: Change all occurrences of 7, 8 or 9 into 0, 1 and 2, respectively. Step two take the left most digit and change it to the next digit in the sequence step three add that digit to the next digit along step 4 replace the left 2 most digits with result step 5 repeat from one with the exception first if left most digit is 7 drop it unless it's the only digit at which point it's zero
Once you have a digit less then 7, if =0 then it's divisible by 7 otherwise the digit that is left is how much bigger then 7 it is.
