3 years, 7 months ago
3 years, 7 months ago
Looking at the prime factorization of 75 ,a number will be divisible by 75 if it is divisible by 25 and 3.For divisibility of number by 5 ^n, number formed by last n digits of the number should be divisible by 5^n(analogous rule applies to 2^n also ).For example when n=2 ,the number will be divisible by (5^2)25, if the number formed by last 2 digits is divisible by 25.They can be any of the following->25,50,75 ,00.In this case since penultimate digit is 7 so y=5 For divisibility by 3, the sum of digits should be divisible by 3 so x+51 should be divisible by 3.Hence x can be either of 3,6,9,0.