Gmat_mission wrote:What is the units digit of 248^20?
A. 0
B. 2
C. 4
D. 6
E. 8
When 8 is raised to consecutive powers, the unit digit repeat in a CYCLE OF 4:
8¹ --> units digit of 8.
8² --> units digit of 4. (Since the product of the preceding units digit and 8 = 8*8 = 64.)
8³ --> units digit of 2. (Since the product of the preceding units digit and 8 = 4*8 = 32.)
8� --> units digit of 6. (Since the product of the preceding units digit and 8 = 2*8 = 16.)
From here, the units digits will repeat in the same pattern: 8, 4, 2, 6.
Thus, the units digit repeat in a CYCLE OF 4.
Implication:
When an integer with a units digit of 8 is raised to a power that is a multiple of 4, the units digit will be 6.
Since 248²� has a units of 8 and an exponent that is a multiple of 4, the units digit = 6.
The correct answer is
D.
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