answer it plz !!!!!

Test Preparation
1

<p>if a is a set of prime numbers and b is the set of two digit positive integers whose unit digit is 5 , how many numbers are common to both sets ?
(A) none
(b) one
(c) two
(d) five<br>
(e) nine </p>

<p>answer is (a)<br>
i solved in this way ( prime numbers :- 2-3-5-7-1-13-19-23-29)<br>
since the unit digit is 5 and 5 is not prime so there no any common number between the two sets ? is this way of solving right</p>

2

<p>Ask you math teacher.</p>

3

<p>It’s ok to reason it this way if you include all the two-digit numbers in your set (I.e. don’t stop at 29 but at 97).</p>

<p>It’s better to notice that all numbers which end in 5 must have 5 as a factor. Therefore the only prime number ending in 5 is 5 itself. And since 5 has only one digit, the answer is none.</p>