Variables Math Question

Test Preparation SAT Preparation
1

<p>The question is from McGraw's 12 Practice Tests for SAT. </p>

<p>20.) Each of the k girls in a club agreed to raise an equal amount of money to give to a charity to which the club had pledged a total of x dollars. If p more girls later join the club and also agree to raise an equal share of the pledged amount, how much less would each of the
original club members have to raise, in dollars, than she had originally agreed to raise?</p>

<p>a) x/k
b) x/(k+p)
c) px/(k+p)
d) x(k+p)/k
e) px/k(k+p)</p>

<p>Originally, I had chosen k to equal 5 and x to equal 20. Therefore, each student was paying $4. After, I had p = 5 so that there would be a total of 10 students, and therefore, each student would then pay $2. This meant that every student paid $2 left. When plugging in my numbers into the equations, B worked as 20/(5+5)=2. Unfortunately, the correct answer was E. When plugging in my variables, I could see that both E and B work. So for the future, should I always just try to pick different values for each variable?</p>

2

<p>You were doing everything right. But when you use this strategy (making up #s for variables) you always have to check all of the answers. And when two of them work, just go back, change one of your numbers, find your new answer and then recheck the answers that worked the first time.</p>

<p>If you don’t want to do that, the other thing you can do (besides algebra!) is make a point of picking slightly unusual numbers. The numbers that make the math the most obvious are the ones that the SAT often will make more than one answer to match.</p>