<p>I have a question about the second blue book, practice test 10, section 5 (a math section) number 14 on page 969.</p>
<p>I'm confused as to what the question is asking. I'll post the question for those of you that don't have the book...</p>
<p>How many integers greater than 20 and less than 30 are each the product of exactly two different (different is underlined) numbers, both of which are prime?</p>
<p>a)zero
b)one
c)two
d)three
e)four</p>
<p>Since it says exactly two different numbers, is the question essentially asking how many integers between 20 and 30 are prime?</p>
<p>21 = 3<em>7…YES
22 = 2</em>11…YES
23 = prime so NO
24 = 1,2,3,4,5,8,12,24 so NO
25 = 5<em>5, but they’re not different so NO
26 = 2</em>13…YES
27 = 3<em>9 but nine isn’t prime so NO
28 = 2</em>19…YES
29 = prime so NO</p>
<p>There are 4. Is the answer E?</p>
<p>
</p>
<p>Nope. I’ll try to rephrase the question:</p>
<p>How many integers between 20 and 30, exclusive, are the product of two distinct prime numbers? </p>
<p>So, go through and check each number.
[ul]
[<em>]21 7</em>3 Both are prime, so this qualifies as an answer.
[<em>]22 11</em>2 Both are prime, so this qualifies as an answer.
[<em>]23 Prime, so it cannot qualify.
[</em>]24 12<em>2; 6</em>4; 24<em>1;3</em>8 There is at least one non-prime number is each pair, so this does not qualify.
[<em>]25 5</em>5 The numbers are prime but not distinct.
[<em>]26 13</em>2 This qualifies.
[<em>]27 Number is prime.
[</em>]28 14<em>2; 7</em>4<br>
[li]29 Number is prime.[/li][/ul]Total of three qualifying numbers.</p>
<p>No, im pretty sure the answer is (D). .</p>
<p>@phasmatis: Here’s the error you made: 2 *19 doesn’t equal 28, but rather 38. </p>
<p>SO THERE’S ONLY 3. Im sure.</p>
<p>
</p>
<p>Ah, what calculators have done. :)</p>
<p>yeah…sorry for the typo…it’s three…thanks</p>
<p>Dang it! Silverturtle got to it first!</p>
<p>Ah, what calculators have done. </p>
<p>LOL.</p>
<p>yeah…these are the types of stupid mistakes that screw me over on the actual test.</p>