The decimal point is placed after two digits starting from the end. For each decimal place, we can write the number divided by 100.
21.12 can be written as
.
Divide the numerator and denominator by 2:
![(2112)/(100)= (156)/(50)](https://img.qammunity.org/2019/formulas/physics/high-school/xsvtxmjoymxbjz9wlqbnb0p2n3ngl9xqy0.png)
The numerator and denominator can be divided by 2 again:
![(78)/(25)](https://img.qammunity.org/2019/formulas/physics/high-school/itmevawq6dq6gssi0nygf50ghitd10z9kl.png)
There is no other common factor between numerator and denominator other than 1. Hence, it is the reduced form.