Let a fraction be 312/168312168.
Normally, as numerator and denominator are even, we will divide each by 22 and then again check numerator and denominator and use divisibility rule to examine the number that can divide them further.
This will go on till they cannot be divided any further by a number other than 11.
On the contrary if we take GCF of 312312 and 168168, we can divide numerator and denominator by GCF and we will get simplified fraction. In above case, GCF is 2424 and dividing by 2424, we get
312/168=(13xx24)/(7xx24)=13/7312168=13×247×24=137
In earlier method it would have been
312/168=(2xx156)/(2xx84)=156/84=(2xx78)/(2xx42)=78/42312168=2×1562×84=15684=2×782×42=7842
= (2xx39)/(2xx21)=39/21=(3xx13)/(3xx7)=13/72×392×21=3921=3×133×7=137