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27 Jan 2021, 03:45
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D
Be sure to select an answer first to save it in the Error Log before revealing the correct answer (OA)!
Difficulty:
55%
(hard)
Question Stats:
65% (02:36) correct
35%
(02:56)
wrong
based on 81
sessions
History
Date
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Not Attempted Yet
The average height of 13 girls in a class is \(144 \frac{8}{13}\) cm. The average height of 11 boys in the class is \(169 \frac{5}{11}\) cm. There are only 24 students in the class. What is the overall average height (in cm) of all the students together in the class?
(A) 133
(B) 143
(C) 156 3/4
(D) 156
(E) 166
(A) 133
(B) 143
(C) 156 3/4
(D) 156
(E) 166
27 Jan 2021, 09:11
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Bunuel
The average is \(13*144 \frac{8}{13} + 11*169 \frac{5}{11}\) divided by 24.
\(Sum = 13*144 + 8 + 11 * 169 + 5\)
\(= 13*144 + 13 + 11*169 \)
\(= 13*(144 + 1 +11*13) \)
\(= 13*(144 + 1 + 143) = 13*144*2\)
Divide by 24 = 2*12 to get \(13*144*2 / (12*2) = 13*12 = 144+12 = 156\).
Ans: D
27 Jan 2021, 09:30
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Since the average weights for both girls and boys are bigger than 144, the answer choices A and B are out. Since there are more girls (13 girls) than boys (11 boys), the average of the class will be slightly lower than 144+(169-144)/2=156.5
So answer choices C and E are also out. The only remaining answer D is the correct answer.
So answer choices C and E are also out. The only remaining answer D is the correct answer.
