<p>A group of 4th graders and 5th graders is going on a field trip to the zoo. Only 20% of the students remembered to bring written permission from their parents. If 40% of the students are 4th graders and 25% if the 4th graders remembered to bring written permission, what percentage of the students are 5th graders who forgot to bring written permission?</p>
<p>A) 10%</p>
<p>B) 30%</p>
<p>C) 50%</p>
<p>D) 60%</p>
<p>E) 80%</p>
<p>The answer is C, but I dont understand this, can some one please explain, the book doesnt even explain it, it says "Set up a chart" which I did but I am still dumbfounded. Thanks.</p>
<p>OK. Assume that the total number of students is 1000. This implies that there are 400 4th graders, and 600 5th graders.</p>
<p>25% of 4th graders got permission --> 100 kids
20% of total kids got permission --> 200 kids
Therefore, 100 5th graders got permission.
This implies that 500 5th graders didn't get permission. 500 kids = 50% = C.</p>
<p>Hope this helps :).</p>
<p>although i don't know the "smart" way of doing this problem, i still got the answer by plugging in numbers.</p>
<p>Lets say 100 students total - Both 5th+4th</p>
<p>20 students out of the all brought permission.</p>
<p>40 students are 4th graders which means only (25%) 10 4th graders remembered to bring permission.</p>
<p>20-10= only 10 5th graders brought permission. so 60-10=50 5th graders who forgot permission.</p>
<p>the question asks for the percentage of the total amount of students are 5th graders who forgot permission so put 50/100= 50%</p>
<p>Let x be the total amount of students (0.4*x* fourth-graders and 0.6*x* fifth-graders). We know that 0.2*x* brought permission slips and that ( 0.4 * 0.25 )x, or 0.1*x*, fourth-graders brought permission slips. That means that 0.1*x* fifth-graders must also have brought permission slips; that is 1/6 of the total amount of fifth graders (0.1 / 0.6). So 5/6 of the fifth graders did not bring permission slips. 0.5*x* / 1*x* = 50%.</p>
<p>To understand these problem always breakdown the question step by step</p>
<p>4th graders = a
5th graders = b</p>
<p>40% of (a + b) = a (40% of the students are 4th graders)
60% of (a + b) = b (60% of the students are 5th graders)</p>
<p>25% of [40% x (a + b)] = 0.1(a + b)==> 0.1 is the same as 10%, so 10% of 4th graders remembered to bring written permission.</p>
<p>20% of the students remembered to bring written permission from their parents.So that other 10% who remembered to bring written permission from their parents must be 5th graders.</p>
<p>If 60% of the students are 5th graders and 10% of 5th graders remembered to bring written permission from their parents, then 60% - 10% = 50% who did not remembered to bring written permission.</p>
<p>Thanks guys, I get it now, but I realized that once I found the number of 5th graders did not get their permission slips, I just got the percentage of 5th graders from the 5th graders themselves, not 4th and 5th combined, so I was confused when I got 83.334%.</p>
<p>Ha, I was proud that I got this problem. However, I won't eleborate on how, because everyone else here has done an above adequate job doing it. :)</p>