How many positive four-digit integers n have the property that the three-digit number obtained by removing the leftmost digit is one-fifth of n?
Is this what you want?
1250, 2500, 3750 >> Total = 3 such numbers:
250 / 1250 = 1 / 5, 500 / 2500 = 1 / 5, 750 / 3750 = 1 / 5
They are the only ones.