The way to write four sevens with simple arithmetical signs so that they
represent 100 is as follows:--
7 7
-- × -- = 100.
.7 .7
Of course the fraction, 7 over decimal 7, equals 7 divided by 7/10,
which is the same as 70 divided by 7, or 10. Then 10 multiplied by 10 is
100, and there you are! It will be seen that this solution applies
equally to any number whatever that you may substitute for 7.