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Please help!! I don’t know how to solve this. Which one is the digit of the units in 3^81:

A) 3
B) 9
C) 7
D) 1
E) None of the above

Respuesta :

Solution:

  • 3⁸¹ = 3⁹ ⁺ ⁹ ⁺ ⁹ ⁺ ⁹ ⁺ ⁹ ⁺ ⁹ ⁺ ⁹ ⁺ ⁹ ⁺ ⁹ ⁺ ⁹
  • 3⁸¹ = 3⁹ x 3⁹ x 3⁹ x 3⁹ x 3⁹ x 3⁹ x 3⁹ x 3⁹ x 3⁹
  • 3⁹ = 19683 [Using Calculator]

This means that the Unit digit of 19683 is 3. For each number, multiply the unit's digit of 3⁹.

  • 3 x 3 x 3 x 3 x 3 x 3 x 3 x 3 x 3
  • => 19683
  • => Unit digit of 3⁸¹ = 3

Option A is correct.

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