Given: (101×72)2 Concept: If (101×a) , then ⇒[(100+1)×a] ⇒(100a+a) Calculation: (101×72)2 ⇒[(100+1)×72)2 ⇒(7200+72)2 ⇒(7272)2 ⇒ 52881984 ∴(101×72)2=52881984 . Smart Method: (101×72)2 Taking unit digits (1×2)2 ⇒22 ⇒ 4 Hence, answer must have 4 at its unit digit. ∴ 52881984 is the correct option.