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At a certain school, the ratio of the number of second grade [#permalink]
 27 Feb 2012, 10:02
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At a certain school, the ratio of the number of second graders to the number of fourth graders is 8 to 5, and the ratio of the number of first graders to the number of second graders is 3 to 4. If the ratio of the number of third graders to the number of fourth graders is 3 to 2, what is the ratio of the number of first graders to the number of third graders? A. 16 to 15 B. 9 to 5 C. 5 to 16 D. 5 to 4 E. 4 to 5
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Re: At a certain school, the ratio of the number of second grade [#permalink]
27 Feb 2012, 13:17
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BANON wrote: At a certain school, the ratio of the number of second graders to the number of fourth graders is 8 to 5, and the ratio of the number of first graders to the number of second graders is 3 to 4. If the ratio of the number of third graders to the number of fourth graders is 3 to 2, what is the ratio of the number of first graders to the number of third graders?
A. 16 to 15
B. 9 to 5
C. 5 to 16
D. 5 to 4
E. 4 to 5 Let # of first, second, third and fourth graders be A, B, C and D respectively. Question: \frac{A}{C}; Given: \frac{B}{D}=\frac{8}{5}, \frac{A}{B}=\frac{3}{4}, and \frac{C}{D}=\frac{3}{2}; Equate D's: \frac{B}{D}=\frac{8}{5}=\frac{16}{10} --> \frac{C}{D}=\frac{3}{2}=\frac{15}{10}. Now, equate B's: \frac{A}{B}=\frac{3}{4}=\frac{12}{16}; \frac{A}{C}=\frac{12}{15}=\frac{4}{5}. Answer: E.
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Re: At a certain school, the ratio of the number of second grade [#permalink]
22 Apr 2012, 02:23
How can you solve this with an unknown multiplier?
let a=1st b=2nd c=3rd and d=4th graders
b/d=8/5 or b=8x and d=5x
so we get a=3/4*(8x)=6x and c=15/2*x
which obviously is not correct, why can't I apply this concept here?
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Re: At a certain school, the ratio of the number of second grade [#permalink]
22 Apr 2012, 02:31
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At a certain school, the ratio of the number of second graders to the number of fourth graders is 8 to 5, and the ratio of the number of first graders to the number of second graders is 3 to 4. If the ratio of the number of third graders to the number of fourth graders is 3 to 2, what is the ratio of the number of first graders to the number of third graders?
(A) 16 to 15
(B) 9 to 5
(C) 5 to 16
(D) 5 to 4
(E) 4 to 5
The explanation in the OG is convoluted. What's the shortcut to solving this?
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Re: Comparing Ratios [#permalink]
13 Sep 2012, 08:37
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Re: At a certain school, the ratio of the number of second grade [#permalink]
17 Jan 2013, 02:40
1-2 is 3:4 ----(a) 2-4 is 8:5 ----(b) which means (aX2) 1-4 is 6:5 ----(c) 4-3 is 2:3 ----(d) which means (cX2 & dX5) 1-3 is 12:15 or 4:5
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Re: At a certain school, the ratio of the number of second grade
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17 Jan 2013, 02:40
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