GATE | GATE CS Mock 2018 | Set 2 | Question 8

The units digit of (35)87 + (93)46 is:

(A) 4
(B) 2
(C) 6
(D) None of these


Answer: (A)

Explanation: Unit digit will only depend on the unit digit of 35 and 87.
For the first part (35)87 , unit digit will only depend on 5. And for every power of 5 it will end only with 5. ——– (i)
And for second part (93)46 ,here unit digit is 3 and cyclicity for 3 is 4,it means that after every 4th power unit digit will repeat.
When will divide the power 46 with 4 we get the remainder as 2. And hence 32 is 9. ———(ii)
Now from equation (i) and (ii)
we have, 5+9 = 14
Hence, the unit digit is 4.
Option A is correct.

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