GRE Prep Club Daily Prep
Thank you for using the timer - this advanced tool can estimate your performance and suggest more practice questions. We have subscribed you to Daily Prep Questions via email.
Customized
for You
Track
Your Progress
Practice
Pays
Not interested in getting valuable practice questions and articles delivered to your email? No problem, unsubscribe here.
If n is a two-digit number, in which n = x^y. If x + y < 8,
[#permalink]
26 Oct 2017, 23:49
26 Oct 2017, 23:49
3
2
9
Bookmarks
00:00
Question Stats:
29% (02:09) correct
70% (01:53) wrong based on 121 sessions
Hide Show timer Statistics
If n is a two-digit number, in which n = x^y. If x + y < 8, and x and y are positive integers greater than one, then the units digit of n could be which of the following?
(A) 0
(B) 1
(C) 2
(D) 3
(E) 4
(F) 5
(G) 6
(H) 7
(I) 8
(J) 9
Kudos for correct solution.
(A) 0
(B) 1
(C) 2
(D) 3
(E) 4
(F) 5
(G) 6
(H) 7
(I) 8
(J) 9
Kudos for correct solution.
Show: :: OA
(B), (C), (E), (F), (G) and (H).
ShowHide Answer
Official Answer
B,C,E,F,G,H
Re: If n is a two-digit number, in which n = x^y. If x + y < 8,
[#permalink]
27 Oct 2017, 05:00
27 Oct 2017, 05:00
4
1
Bookmarks
x and y are strictly greater than 1 and their sum is less than 8, thus we are left with numbers 2, 3, 4, 5 so as they are all above 1 and their sum is 7 at maximum. Then, we can mix them using the fact that n = x^y.
In this way,
2^4 = 16 so (G)
2^5 = 32 so (C)
3^3 = 27 so (H)
3^4 = 81 so (B)
4^3 = 64 so (E)
5^2 = 25 so (F)
since we have to look at the unit digits!
In this way,
2^4 = 16 so (G)
2^5 = 32 so (C)
3^3 = 27 so (H)
3^4 = 81 so (B)
4^3 = 64 so (E)
5^2 = 25 so (F)
since we have to look at the unit digits!
General Discussion
Re: If n is a two-digit number, in which n = x^y. If x + y < 8,
[#permalink]
27 Oct 2017, 10:52
27 Oct 2017, 10:52
3
Bunuel wrote:
If n is a two-digit number, in which n = x^y. If x + y < 8, and x and y are positive integers greater than one, then the units digit of n could be which of the following?
(A) 0
(B) 1
(C) 2
(D) 3
(E) 4
(F) 5
(G) 6
(H) 7
(I) 8
(J) 9
Kudos for correct solution.
(A) 0
(B) 1
(C) 2
(D) 3
(E) 4
(F) 5
(G) 6
(H) 7
(I) 8
(J) 9
Kudos for correct solution.
Show: :: OA
(B), (C), (E), (F), (G) and (H).
Here
X cannot be greater than 5 , because if X= 6 then y can neither be 1 nor 2 as this will nullify the statement.
therefore the possible values are
x=2 then y=5,4 i.e \(2^5\), \(2^4\) = 32 , 16 (\(2^3\), \(2^2\) are not two digit number)
x=3 then y=3,4 i.e \(3^3\) , \(3^4\) = 27, 81
x=4 then y=2,3 i.e \(4^2\) , \(4^3\) = 16 , 64
x=5 then y=2 i.e \(5^2\) = 25
Thus the unit digit are = 1,2,4,6,7
