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The average (arithmetic mean) score of a class was 70. If the boys av
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20 Oct 2023, 03:54
20 Oct 2023, 03:54
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The average (arithmetic mean) score of a class was 70. If the boys’ average was 65 and that of girls’ was 80, what could be the number of boys and girls, respectively, in the class?
(A) 8; 9
(B) 18; 27
(C) 9; 18
(D) 18; 9
(E) 5; 2
(A) 8; 9
(B) 18; 27
(C) 9; 18
(D) 18; 9
(E) 5; 2
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Free Materials for the GRE General Exam - Where to get it!!
GRE Geometry Formulas
GRE - Math Book
Re: The average (arithmetic mean) score of a class was 70. If the boys av
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20 Oct 2023, 11:46
20 Oct 2023, 11:46
1
To answer this question quickly, we can see that the two scores of 65 (boys) and 80 (girls) average to be 70 which is closer to the boys average score. Knowing this information, there needs to be more boys in the class to make the overall average closer to theirs. This eliminates answer choices A-C.
To determine the correct answer we can plug in the remaining answer choices into an average formula: (65b+80g)/b+g should equal 70
Answer choice D: ((65*18)+(80*9))/(18+9) = (1170+720)/27 = 70
Answer choice E: ((65*5)+(80*2))/(5+2) = (325+160)/7 = 69.3
This makes D the correct answer.
Posted from my mobile device
To determine the correct answer we can plug in the remaining answer choices into an average formula: (65b+80g)/b+g should equal 70
Answer choice D: ((65*18)+(80*9))/(18+9) = (1170+720)/27 = 70
Answer choice E: ((65*5)+(80*2))/(5+2) = (325+160)/7 = 69.3
This makes D the correct answer.
Posted from my mobile device
Re: The average (arithmetic mean) score of a class was 70. If the boys av
[#permalink]
20 Oct 2023, 15:28
20 Oct 2023, 15:28
1
Both average= 70
Girls average = 80
Boys average = 65
65 ——— 70 ——— 80
Difference of boys average from both average: 70-65= 5
Difference of girls average from both average: 80-70 = 10
Form a ratio by flipping the numbers and putting them on top of each others.
10/ 5 or 2/1.
So there are 2 boys for every 1 girl.
Answer: D
Posted from my mobile device
Girls average = 80
Boys average = 65
65 ——— 70 ——— 80
Difference of boys average from both average: 70-65= 5
Difference of girls average from both average: 80-70 = 10
Form a ratio by flipping the numbers and putting them on top of each others.
10/ 5 or 2/1.
So there are 2 boys for every 1 girl.
Answer: D
Posted from my mobile device
