let a , b , c be distinct digits . consider a two - digit number ‘ ab ’ and a 3 - digit number ‘ ccb ’ , both defined under the usual decimal number system , if ( ab ) 2 = ccb > 300 , then the value of b is  Choose one.
A) 1 B) 0 C) 5 D) 6 E) 7

Rationale: explanation : given , ( ab ) 2 = ccb . [ only 1 , 5 and 6 on squaring will result with same digits in units place . ] taking a = 2 , b = 1 , = > ( 21 ) ^ 2 = 441 > 300 . hence , the required value of b = 1 answer : a
Answer: A