For any natural number x, (18)8x−(7)8x is divisible by:
1) 25 2) 373 3) 11 4) 275
1,2,3
1,2,4
only 1,2
1,2,3 and 4
8x is even. Hence it will be divisible by 18−7,18+7,182+72,182−72. Answer is option (d).
Question 192
Using each of the digits 1,2,3 and 4 only once, determine the smallest 4-digit number divisible by 4.