Question

The number 123 x is divisible by 7 find out the value of the digit x if the number is also is divisible by 3

Answer 1

the ans is 21.. in the question it's given that x is divisible by 3. so x can me one of the multiples of 3. thus, we multiply 123 by a multiple of 3, in other words we calculate the value if 123x when is a multiple of 3. on putting the value 3, 6, 9, 12,15,18 we don't get number which is divisible by 7.. but when we have x= 21, we get 123x= 123×21 = 2583.. on diving 2583 by 7, we get the quotient as 369.so, 2583 is divisible by 7. hence the ans is 21