Explain this problem to me please

Test Preparation SAT Preparation
1

<p>Hey everyone…i know i’ve been been ODing on cc today but explain to me how D is wrong. Thanks…and rate my essays if you can :slight_smile: <a href=“Critique my essay please - SAT Preparation - College Confidential Forums”>Critique my essay please - SAT Preparation - College Confidential Forums; and <a href=“http://talk.collegeconfidential.com/sat-preparation/519676-what-would-you-give-essay.html[/url]”>http://talk.collegeconfidential.com/sat-preparation/519676-what-would-you-give-essay.html&lt;/a&gt;&lt;/p&gt;

<p>The average(arithmetic mean) of nine numbers is 9. When a tenth number is added the average of the ten numbers is also 9. What is the tenth number ?</p>

<p>a) 0
b) 9/10
c) 10/9
d) 9
e) 10 </p>

<p>A.
Eliminate some obvious wrong ones B. , C., E. Remember to always estimate and have a good rough estimate of where the answers should be which is right around the original average of 9; if you added a new number that was much higher or lower like say 0 or 1,000 the average could never remain 9.</p>

<p>TEST TRAP: D is atrap and since you’re not dealing with the first few problems you should not have gone on without really thinking about his one</p>

2

<p>it isn’t wrong…</p>

<p>9x9 = 81</p>

<p>and 9x10 = 90</p>

<p>it should be 9…</p>

<p>unless it says the average of the nine numbers is also 9 and not ten</p>

3

<p>doH 10char</p>

4

<p>that makes no sense… the average of 9 numbers is 9 =</p>

<p>the sum = 9x9 = 81</p>

<p>the average of 10 numbers is also 9</p>

<p>the sum must be = 9x10 = 90</p>

<p>90-81 = 9</p>

<p>the last number should be 9</p>

5

<p>yea i was just trying to make sure i wasnt the crazy one…lol…i hope i didnt waste anyone’s time…evaluate my essays plz!</p>

6

<p>Wow, where did you get this problem from? If it’s from a book, I’d go to the store and demand my money back.</p>

7

<p>I did my calculations, and it <em>has</em> to be 9…</p>

<p>9 x 9 = 81</p>

<p>(81 + x)/(9 + 1)
^^ Substitute 9 in for x</p>

<p>90/10 = 9</p>

8

<p>exactly… where is this book from?</p>

<p>It seems to be a load of crud</p>