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Of the test animals in a laboratory, 60% are brown rats and 40% are 29 Aug 2017, 23:52
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85% (01:36) correct 15% (01:19) wrong based on 113 sessions

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Of the test animals in a laboratory, 60% are brown rats and 40% are black rats. If the average brown rat weighs 9.2 ounces and the average black rat weighs 7.7 ounces, what is the average weight of a rat in the laboratory?

A. 7.7 ounces
B. 8.1 ounces
C. 8.45 ounces
D. 8.6 ounces
E. 9.2 ounces
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D
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Of the test animals in a laboratory, 60% are brown rats and 40% are 30 Aug 2017, 00:09
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Bunuel
Of the test animals in a laboratory, 60% are brown rats and 40% are black rats. If the average brown rat weighs 9.2 ounces and the average black rat weighs 7.7 ounces, what is the average weight of a rat in the laboratory?

A. 7.7 ounces
B. 8.1 ounces
C. 8.45 ounces
D. 8.6 ounces
E. 9.2 ounces
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Suppose their are 10 rats
(9.2*6 + 7.7*4)/10 = (55.2+30.8 = 86)/10 = 8.6
D
9.2-7.7 = 1.5 divided in 6:4 ratio would be 0.9 and 0.6
9.2-0.6 = 8.6
D
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Of the test animals in a laboratory, 60% are brown rats and 40% are 30 Aug 2017, 00:12
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0.6*9.2+0.4*7.7=5.52+3.08=8.6 so D is correct

Goal+Plan=Success (GPS)
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Of the test animals in a laboratory, 60% are brown rats and 40% are 30 Aug 2017, 00:30
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Bunuel
Of the test animals in a laboratory, 60% are brown rats and 40% are black rats. If the average brown rat weighs 9.2 ounces and the average black rat weighs 7.7 ounces, what is the average weight of a rat in the laboratory?

A. 7.7 ounces
B. 8.1 ounces
C. 8.45 ounces
D. 8.6 ounces
E. 9.2 ounces
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- Let the number of total animal : 100, so brown rats (BR) = 60 and black rats (BL) = 40.
- \(Average weight = \frac{{number of BR}*{BR's average weight}+{number of BL}*{BL's average weight}}{Total Animal} = \frac{(60*9.2)+(40*7.7)}{100} =\) 8.6 ounces.

D.
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Of the test animals in a laboratory, 60% are brown rats and 40% are 31 Aug 2017, 11:03
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Bunuel
Of the test animals in a laboratory, 60% are brown rats and 40% are black rats. If the average brown rat weighs 9.2 ounces and the average black rat weighs 7.7 ounces, what is the average weight of a rat in the laboratory?

A. 7.7 ounces
B. 8.1 ounces
C. 8.45 ounces
D. 8.6 ounces
E. 9.2 ounces
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No need to calculate.

If we have equal number of rates, it means average wight will be in the middle = 8.45. However, there is greater number of brown rats, So the average will tend be slightly higher than 8.45. So it will be 8.6

Answer: D
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Of the test animals in a laboratory, 60% are brown rats and 40% are 31 Aug 2017, 11:21
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Let the number of rats be x

It has been given the brown rats are 60%(average weight - 9.2)
Also, the black rats are 40%(weight weight - 7.7)

From the questions stem, \(\frac{.6x * 9.2 + .4x * 7.7}{x} =\frac{5.52x + 3.08x}{x} = 8.6\)(Option D)
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Of the test animals in a laboratory, 60% are brown rats and 40% are 02 Sep 2017, 07:29
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Bunuel
Of the test animals in a laboratory, 60% are brown rats and 40% are black rats. If the average brown rat weighs 9.2 ounces and the average black rat weighs 7.7 ounces, what is the average weight of a rat in the laboratory?

A. 7.7 ounces
B. 8.1 ounces
C. 8.45 ounces
D. 8.6 ounces
E. 9.2 ounces
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We create the following equation for a weighted mean:

0.6(9.2) + 0.4(7.7) = 5.52 + 3.08 = 8.6

Do we have to write questions about test animals in laboratories? Isn’t there a better theme that we can come up with?

Answer: D
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