<p>I have a feeling this is really easy but for the life of me I cannot figure this out. The explanations at the back of the book are not helping. Can someone explain this please?</p>
<hr>
<p>If the price of a certain product is increased by 15 percent, by approximately what percent must the new price be reduced to obtain the original price? </p>
<p>a) 13 b) 15 c) 17 d) 85 e)115</p>
<p>(from PR 11 Practice Tests for the SAT, Test #7 S5 #8)
The answer is a) 13.</p>
<p>Plug in:
Let say the original price is 100. Increased by 15% is 115.
115x=100
x=100/115
x=0.87 </p>
<p>0.87*100=87%
100-87=13%</p>
<p>Let’s say the original price is $100.
An increase of 15% would bring it to $115.</p>
<p>K.</p>
<p>So like, the question is asking by how much you’d have to reduce 115 to get 100.</p>
<p>115 x .87</p>
<p>That translates to: “87% of 115”
and becomes 100.</p>
<p>Thus, you reduced the $115 by 13%.</p>
<p>I’m so bad at explaining lololol.</p>
<p>Oh I see how to solve this now 
thanks to both of you guys!</p>
<p>Looks like you’ve got it all figured out here, but for anyone else who reads this:</p>
<p>General rule for percent questions: PLUG IN 100!!! This kind of question appears on the SAT all the time, and can almost always be solved this way.</p>
<p>Before you do anything, glance at the possible answers. You can quickly rule out 85 and 115 with a moment’s thought; neither will bring an increase of 15% back anywhere near the original value. They’re just traps for the unskilled; one is 100% - 15%, one is 100% + 15%.</p>
<p>The other 3 them cluster around the 15% increase. So without having to do any math, the problem boils down to asking you if you exactly reverse a 15% increase with the same reduction, slightly more, or slightly less. This is what to ask yourself.</p>
<p>Start with the middle answer as a guess; if you take a number and increase it by 15% to get a new number, is 15% of the new number less than, the same as, or more than the previous increase? If its the same as the previous increase, then a 15% reduction puts you right back where you were before. </p>
<p>But just by thought you can see it has to be more by doing a bit of almost-math in your head. Start with 100; a 15% increase gives you 115. You can instantly perceive that 15% of 115 has to be more than 15, since 15 was the answer to 15% of 100 and 115 is a bigger number.</p>
<p>So reducing the price by 15% will cause you to undershoot the original value. You need to reduce by slightly less than 15%, and the only answer that does this is 13%</p>
<p>Can you give me the answer keys of this section? I lost them</p>