<p>Only tenth-, eleventh-, and twelfth-grade students atten Washington High School. The ratio of tenth graders to the school's total student population is 86:225, and the ratio of eleventh graders to the school's total student population is 18:51. If 1 student is chosen at random from the entire school, which grade is that student most likely to be in?</p>
<p>I did:</p>
<p>86/225 = 38.2% chance of tenth grade
18/51 = 35.2% chance of eleventh grade
100-(38.2+35.2) = 26.6% chance of twelfth grade</p>
<p>So, i chose tenth grade, but the answer is eleventh grade. What am I doing wrong?</p>
<p>It’s from a released exam from a few years ago. My sister had taken the test in June and ordered her booklet, and I just finished the math test. The key says the answer is eleventh graders, but I can’t figure out why!</p>
<p>That would really suck if the answer key was wrong when they scored everything, because that would kind of explain why my math score is only so low. I took it in June too.
I’m skeptical as to that being the case on the actual test, but I guess you never know.</p>
<p>Are you sure that the ratio of tenth grade to class pop isn’t 86/255 because that would make more sense since 51x5=255. Ussually they try to make the answers turn out nice and neat, maybe you misread</p>
<p>It’s 86/255 - I made the same mistake when I did this problem. I put 225 in my calculator instead of 255. I got the same answer as you - trust me it’s 86/255.</p>