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If a is an integer and 0 < a < 7 and b = a^7, then what is the value

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Bunuel
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If a is an integer and 0 < a < 7 and b = a^7, then what is the value [#permalink] New post   11 Oct 2016, 02:11
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If a is an integer and 0 < a < 7 and b = a^7, then what is the value of b?

(1) a^(-3) > 0.01

(2) a^2 has a units digit of 6.
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msk0657
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Re: If a is an integer and 0 < a < 7 and b = a^7, then what is the value [#permalink] New post   11 Oct 2016, 03:15
Bunuel wrote:
If a is an integer and 0 < a < 7 and b = a^7, then what is the value of b?

(1) a^(-3) > 0.01

(2) a^2 has a units digit of 6.


Stat 1: 1/a^(3) > 0.01 for a 1 to 6...We get 1/a^(3) > 0.01...not exact value....Insufficient.

Stat 2: only 4 and 6 have 6 as units digits...two values insufficient.

Both : We still have two values...Insufficient.

IMO option E..
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Re: If a is an integer and 0 < a < 7 and b = a^7, then what is the value [#permalink] New post   11 Oct 2016, 03:46
IMO C, cos from stat2 it can be 4 or 6. And combining it with stat2, we get 4


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Re: If a is an integer and 0 < a < 7 and b = a^7, then what is the value [#permalink] New post   11 Oct 2016, 03:58
to calculate b we need the value of and If 0<a<7 then a is 1/2/3/4/5/6.

1. if a^-3>0.01 then 1/a^3 >1/100 so a^3 <100 so a can be 1/2/2/4 only because 5^3 is 125 which is greater than 100 so 1 is not SUFFICIENT
2. unit digit of a^2 6 so a can be 4 (4^2=16) or 6 (6^2=36) Not Sufficient

combining 1 and 2 a is 1/2/3/4 and a is either 4 or 6 a is 4 so answer is C
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Re: If a is an integer and 0 < a < 7 and b = a^7, then what is the value [#permalink] New post   11 Oct 2016, 07:07
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msk0657 wrote:
Bunuel wrote:
If a is an integer and 0 < a < 7 and b = a^7, then what is the value of b?

(1) a^(-3) > 0.01

(2) a^2 has a units digit of 6.


Stat 1: 1/a^(3) > 0.01 for a 1 to 6...We get 1/a^(3) > 0.01...not exact value....Insufficient.

Stat 2: only 4 and 6 have 6 as units digits...two values insufficient.

Both : We still have two values...Insufficient.

IMO option E..


Statement 1 will work only for a = 1 to 4 and not 5 and 6. Please recheck.

So, Answer should be C as we will get a distinct value of a after combining.
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Re: If a is an integer and 0 < a < 7 and b = a^7, then what is the value [#permalink]
11 Oct 2016, 07:07
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Bunuel
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