Bunuel wrote:
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
- Let the number of total animal : 100, so brown rats (BR) = 60 and black rats (BL) = 40.
-\( Average weight =\frac{{number of BR}*{BR's average weight}+{number of BL}*{BL's average weight}}{Total Animal}\)
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