What is the units digit of a positive integer n?

Question

1) The units digit of  n^2  is 4
2) The units digit of  n^3  is 8

elegantm · Answer

Just curious to know, why statement A is Insufficient to answer.

As per statement A, n could be either +2 or -2 and as per question n is a positive integer. Thus combining statement A and question, n =2.

Kindly explain if I am making any mistake.

0akshay0 · Answer

for St I n can be 8 where the units digit of  n^2 = 8^2  is 4
since n can be 2 or 8 St I is insufficient

obliraj · Answer

St. 1- units digit of n can be 2 or 8--- Not sufficient
St. 2- Units digit of n should be 8---- Sufficient.
Answer B.

MathRevolution · Answer

==> In the original condition, there is 1 variable (n) and in order to match the number of variables to the number of equations, there must be 1 equation as well. Since there is 1 for con 1) and 1 for con 2), D is most likely to be the answer. For con 1), from \(n^2\)=~4,you get n=~2, ~8, hence it is not unique and not sufficient. For con 2), from \(n^3\)=~8, you get n=~2, hence it is unique and sufficient.

Therefore, the answer is B.
Answer: B

Therefore, the answer is B.
Answer: B

ablatt4 · Answer

n^2=4
n=2,-2
n^3=8 
n=2

only 2 is sufficient (B)

EthanTheTutor · Answer

Testing n^2=4 doesn't show that statement 1 is not sufficient. "Positive integer n", so -2 isn't a possible value for n. Even if it were, -2 still has a units digit of 2; both cases you found give the same units digit, so if that were the only possibility statement 1 would be sufficient.

ablatt4

n^2=4
n=2,-2
n^3=8
n=2

only 2 is sufficient (B)

What is the units digit of a positive integer n?

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