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Of the final grades received by the students in a certain [#permalink]
20 Jan 2015, 05:04
I guess the more staightforward way to do this is giving a variable for the total number of students, say T:
Then: (1/5)T + (1/4)T + (1/2)T + 10 = T T/5 + T/4 + T/2 + 10 = T (4T + 5T + 10T) / 20 = T - 10 --> we multiplied with the LCM and moved 10 to the other side. 19T = 20 (T - 10) 19T = 20T - 200 T = 200, ANS D
Re: Of the final grades received by the students in a certain [#permalink]
22 May 2015, 23:33
This question can also be solved by TESTing THE ANSWERS.
We're given data on the "breakdown" of grades in a course: 1/5 are A's, 1/4 are B's, 1/2 are C's, and the remaining 10 grades are D's. We're asked for the total number of students in the course.
Let's TEST Answer C: 160 students
Total = 160 1/5 are A's = 32 1/4 are B's = 40 1/2 are C's = 80 Sub-total = 152, which leaves 8 students with D's. This is TOO LOW (there are supposed to be 10 students with D's). Thus we need MORE total students. Eliminate Answers A, B and C.
Since 8 is relatively close to 10, we probably don't need that many more students, so let's TEST D next....
Answer D: 200 students
Total = 200 1/5 are A's = 40 1/4 are B's = 50 1/2 are C's = 100 Sub-total = 190, leaving 10 for D's. This is a MATCH for what we were told, so this MUST be the answer.