Official SAT study guide's answer explanations?

Test Preparation SAT Preparation
1

<p>can someone explain me these questions =</p>

<li><p>Tim wrote a seven digit phone number on a piece of paper. he later tore the paper accidentally and the last two digits were lost. what is the maximum number of arrangements of two digits, using the digits 0 through 9, that he could use in attempting to reconstruct the correct phone number?
the answer is 100, my answer is 90 hahaha</p></li>
<li><p>page 369 number 8
sorry i can’t write the question down coz there’s a graph</p></li>
</ol>

<p>thx!</p>

2

<p>Well, there are 10 digits that could go in the first spot and there are 10 digits that could go in the second spot. 10 X 10 =/= 90.</p>

3

<p>1) That’s too easy…so you shouldn’t have got that wrong.
2) The answer to that had been explained before: <a href=“http://talk.collegeconfidential.com/sat-act-tests-test-preparation/99391-help-collegeboard-blue-book-math-problem.html#post1256608[/url]”>http://talk.collegeconfidential.com/sat-act-tests-test-preparation/99391-help-collegeboard-blue-book-math-problem.html#post1256608&lt;/a&gt;&lt;/p&gt;