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bibha
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cyclicity 20 Aug 2010, 23:56
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What is the last digit of 3^987 ?
• 1
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• 6
• 7
• 9



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cyclicity 21 Aug 2010, 01:19
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bibha
What is the last digit of 3^987 ?
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3 has cyclicity of 4.......

so answer is 7 (d)
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cyclicity 21 Aug 2010, 02:54
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D

reason, 3 has cyclicity of 4.....
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bibha
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cyclicity 21 Aug 2010, 05:40
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I know about it. But, can you please elaborate a little?
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cyclicity 21 Aug 2010, 13:39
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it would be 3 raised to the power 3 which would have 7 as it's unit place
Cyclicity of 3 --
3^1=3,
3^2=9,
3^3=27,
3^4=81,
3^5=243,
.....So on
see the unit place it is 3,9,7,1,3,9,7,1.......and repeats after every 4 power
so divide 987 by 4 remainder is 3. Therefore, 3^3 has unit place digit as 7

Let me know if there is still a problem



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