What is the units' digit of (76)^k ?" (1) k is a prime : DS Archive
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# What is the units' digit of (76)^k ?" (1) k is a prime

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Senior Manager
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What is the units' digit of (76)^k ?" (1) k is a prime [#permalink]

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15 Nov 2003, 23:26
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"What is the units' digit of (76)^k ?"
(1) k is a prime integer
(2) k is greater than 2.

please explain your solution. That's the only way to understand the question
Manager
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16 Nov 2003, 06:18
I vote for A.

Since every integer power of 6 results in 6 as the unit digit, it sufficient to know that k is an integer. Whereas Statement (2) doesn't tell us anything about what kind of number k is.
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16 Nov 2003, 06:35
I go with A too. The only case where the units digit is not 6 would be when k is 0 or k is a fraction.
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16 Nov 2003, 07:21
correct.
i was right in disagreeing with the official answer which was D.
thanks
Director
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16 Nov 2003, 12:25
Hallo Vicky think that the answer is correct, no matter what K is the units digit will always be 6...think makes sense P.S: In every case you have 6 multiplied by 6 which is ultimately 6( in units place) no matter what the power is
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16 Nov 2003, 12:45
I agree with BG.
I think asnwer is D
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16 Nov 2003, 12:47
whatever the power be, the unit digit will be "6". so it's D
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16 Nov 2003, 21:50
How can it be A .. coz it states that k is prime ..but 6 is not a prime number....D is right..
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shubhangi

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17 Nov 2003, 03:10
dear freinds.. u have missed one major pioint.
statement 1)
K is a prime number.
Thus whatever be the value of k =2,3,5...
Units digit of (76)^k will always be 6.

Satement 2)
K > 2 . If it was given that k is integer also, then definitely stat. 2 is also suffecient.
what if k = 2.5, 3.5 or any other fraction...!!

Thus 2 is not suffecient.

Hence Ans - A.

ps: Please be cautious in DS questions that involves variables x, y or k.
Check 1: Note down the domain of these variables - positive, negative, or just real numbers.
Check 2: Be sure to check each statement 1 & 2 for all possible values of these variables x, y within the above domain: positive, negative, fractions, underroots, etc...

thx
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17 Nov 2003, 06:00
Hey Vicky,

Where did you find this problem? I hope it's not OG because this would show a major flaw on the ETS' part.
17 Nov 2003, 06:00
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