UPSC 2015 CDS I Math Paper

Remember:
A decimal fraction in which all the digits after the decimal point are repeated is called a pure recurring decimal whereas a decimal fraction in which some digits after the decimal point do not repeat and some digits do is called a mixed recurring decimal.
The period of the decimal representation of

1

p

is a division of p−1
Thus, the decimal form of the vulgarfraction

1

p

is a pure recurring decimal and its period will be some factor of (p−1)