Let x = 15.712 [ 12 bar ] x = 15.712121212............. multiply with 10 both sides , 10x = 157.1212121212..............------(1) again, multiply with 1000 both sides , 1000x = 15712.1212121212...........------(2) subtract equation (2) - (1) 1000x - 10x = 15712.121212.... - 157.121212.... 990x = ( 15712 - 157) = 15555 x = 15555/990 hence, 15555/990 in the form of P/Q of 15.712[ 12 bar