What is the unit digit in (6824)1793 × (3125)317 × (6681)491?
Explanation:
Here, Unit’s digit of 68241793 will be an even number.
Also, Unit’s digit of 3125317 will always by 5.
Hence, Unit’s digit of 5 × even number will always be 0.
⇒ Unit’s digit of (6824)1793 × (3125)317 × (6681)491 = 0.
Alternately,
Unit’s digit of powers of 4 have a cyclicity of 2 terms i.e., unit’s digit follows the pattern of 4 and 6.
⇒ Unit’s digit of 4odd number = 4, and
⇒ Unit’s digit of 4even number = 6.
Unit digit in (6824)1793 = Unit digit in (4)1793 = 4
Also,
Unit digit in (3125)317 = Unit digit in (5)317 = 5
Unit digit in (6681)491 = Unit digit in (1)491 = 1
Required digit = Unit digit in (4 × 5 × 1) = 0.
Hence, option (a).
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