Latest TCS Aptitude Question SOLUTION: WHAT IS UNIT DIGIT OF 2^(3^28439)?

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WHAT IS UNIT DIGIT OF 2^(3^28439)?

Asked In TCS garima sahu (9 years ago)

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MANISH KUMAR SINGH  (9 years ago)

unit digit is 8.

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ravi prakash  (9 years ago)

ans will be 8.
28439/4=7109+3/4
3^3=7*1(3^3=27 and 3^4=81)
so unit place will be 7
now 2^x.....7
after dividing by 4
3 will be remainder
so 2^3=8 in unit place

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neerupama  (9 years ago)

2 as 28439 leaves remainder 3

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Shreyansh  (8 years ago)

Since cyclicity of 3 is 4 (i.e. 3,9,7,1)
so divide 28439 by 4.
28439/4 gives remainder as 3
That implies the unit digit for 3^28439 is 7 (check the cyclicity values).

Now 2^.....7
Since cyclicity of 2 is also 4 (i.e. 2,4,8,6)
divide the power .....7 by 4

for the power .....7 last two digits can be 07, 17, 27, 37, 47, and so on
on dividing these numbers by 4 we either get remainder as 1 or 3
So the answer can be both 2^1= 2 or 2^3= 8

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Manish saini  (9 years ago)

unit digit=8.

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