Problem Solving

P and N are natural numbers. If P^N has the same unit's digit as P, how many possibilities exist for the unit's digit of P?

(A) 1
(B) 2
(C) 3
(D) 4
(E) 5

Would like to know the methodology. OA is D

CaptainHaddock wrote:P and N are natural numbers. If P^N has the same unit's digit as P, how many possibilities exist for the unit's digit of P?

(A) 1
(B) 2
(C) 3
(D) 4
(E) 5

Would like to know the methodology. OA is D

the digits are 0,1,5,6 = 4(d)

CaptainHaddock wrote:P and N are natural numbers. If P^N has the same unit's digit as P, how many possibilities exist for the unit's digit of P?

(A) 1
(B) 2
(C) 3
(D) 4
(E) 5

Would like to know the methodology. OA is D

Well I have a concern here-

1) what is the source of this question?
2) I can give you many more examples in addition to 1,5,6, and 0.

For example if p =3 and N = 5 then 3^5 = 243. this also satisfies the given condition.

If p= 7 and N= 5 then 7^5 = 16807. this also satisfies the given condition.

NONE OF THE OPTIONS SATISFY THIS CONDITION

Again, what is the source of this question?

NONE OF THE OPTIONS SATISFY THIS CONDITION

D is right.

P can take any value and N can take any value

only numbers ending with 0, 1, 5, 6 raised to power of N will have same unit's digit as P