What is the unit digit in the product (3⁶⁵ x 6⁵⁹ x 7⁷¹)?

Explanation:-

Unit digit in 3⁴ = 1 ⇒ Unit digit in (3⁴)¹⁶ = 1
Therefore Unit digit in 3⁶⁵ = Unit digit in [ (3⁴)¹⁶ x 3 ] = (1 x 3) = 3
Unit digit in 6⁵⁹ = 6
Unit digit in 7⁴ ⇒ Unit digit in (7⁴)¹⁷ is 1.
Unit digit in 7⁷¹ = Unit digit in [(7⁴)¹⁷ x 7³] = (1 x 3) = 3
Therefore Required digit = Unit digit in (3 x 6 x 3) = 4.