<p>This question is from Princeton review.
All of the students in the history class are juniors or seniors.There are twice as many girls as boys in the class, and there are three times as many senior girls as junior girls.If a student is selected at random,what is the probability that the student is a junior girl?
Ans- 1/6</p>
<p>Also please tell me are the Princeton teste harder than the usual? I am taking the test this saturday and after doing 12 practice tests from Mcgraw hill my highest score was 1910. But after doing 2 tests from princeton my score is back to 1600-1700. Its really frustating.
Please share your opinions.</p>
<p>I’m not sure about whether the PR book is harder or easier than the real thing, but I strongly recommend that you take at least one test from the Blue Book before Saturday. As to your question: plug in!</p>
<p>Say there are 40 girls. That means 20 boys. If there are 3 times as many senior girls as junior girls, then there are 30 senior girls and 10 junior girls. So there are 10 junior girls out of 60 total kids in the class. Answer: 1/6.</p>
<p>It’s good to attach numbers to some of these questions to make it easier on your head.</p>
<p>60 is good because it’s divisible by a lot of numbers.</p>
<p>Info 1: There are twice as many girls as boys in the class.</p>
<p>Thus, 40 girls, 20 guys.</p>
<p>Info 2: There are three times as many senior girls as junior girls.</p>
<p>From those 40 girls, 30 are senior girls and 10 are junior girls.</p>
<p>Question: How many junior girls are there out of all the students?</p>
<p>10/60 = 1/6</p>
<p>On second thought…maybe it’s more intuitive to plug in starting w/ junior girls!</p>
<p>Say there’s 1 junior girl in the class. That means there are 3 senior girls, for a total of 4 girls in the class. Since there are twice as many girls as boys, there are 2 boys. That’s a total of 6 students, one of whom is a junior girl. Answer: 1/6.</p>
<p>Yeah, I like that better. :)</p>
<p>Haha, PWNtheSAT beat me to it.</p>
<p>lol. how funny that we used the same numbers.</p>