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20 Oct 2014, 11:50
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Be sure to select an answer first to save it in the Error Log before revealing the correct answer (OA)!
Difficulty:
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77% (02:47) correct
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In a certain school, there are 80 Freshmen, 100 Sophomores, and 220 Upperclassmen, drawn from three cities: A, B, and C. Sixty percent of students are from A, 30% from B, the rest from C, and all these students from C are freshmen. Half the student from B are upperclassman, and the rest are split evenly between the other two grades. How many sophomores are from A?
(A) 60
(B) 70
(C) 80
(D) 90
(E) 100
For a discussion of the Double Matrix method for solving questions of this sort, as well as the OE for this question, see:
https://magoosh.com/gmat/2014/gmat-prac ... lems-sets/
Mike
(A) 60
(B) 70
(C) 80
(D) 90
(E) 100
For a discussion of the Double Matrix method for solving questions of this sort, as well as the OE for this question, see:
https://magoosh.com/gmat/2014/gmat-prac ... lems-sets/
Mike
20 Oct 2014, 21:09
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Answer = B = 70
Solved using matrix method as below:
mat.png [ 6.72 KiB | Viewed 6202 times ]
1. Total Freshmen = 80
2. Total Sophomores = 100
3. Total Upperclassmen = 220
4. Net people = 80+100+220 = 400
5. 60% from A \(= \frac{60}{100} * 400 = 240\)
6. 30% from B \(= \frac{30}{100} * 400 = 120\)
7. Remaining from C = 400 - (240+120) = 40
8. All students of C are Freshmen = 40
9. Half the student from B are upperclassman = 120/2 = 60
10. rest are split evenly between the other two grades = 30
11. rest are split evenly between the other two grades = 30
12. How many sophomores are from A = 100 - 30 = 70
Solved using matrix method as below:
Attachment:
mat.png [ 6.72 KiB | Viewed 6202 times ]
1. Total Freshmen = 80
2. Total Sophomores = 100
3. Total Upperclassmen = 220
4. Net people = 80+100+220 = 400
5. 60% from A \(= \frac{60}{100} * 400 = 240\)
6. 30% from B \(= \frac{30}{100} * 400 = 120\)
7. Remaining from C = 400 - (240+120) = 40
8. All students of C are Freshmen = 40
9. Half the student from B are upperclassman = 120/2 = 60
10. rest are split evenly between the other two grades = 30
11. rest are split evenly between the other two grades = 30
12. How many sophomores are from A = 100 - 30 = 70
22 Jan 2015, 23:46
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Ans B = 70
I don't know how to upload the sceenshot but I used 3*3 Matrix
F S U Total
A ? 240
B 30 30 60 120
C 40 0 0 40
Total 80 100 220 400
On solving we get ? = 70
I don't know how to upload the sceenshot but I used 3*3 Matrix
F S U Total
A ? 240
B 30 30 60 120
C 40 0 0 40
Total 80 100 220 400
On solving we get ? = 70
