nidhis.1408 wrote:A publishing company produced a record high of 180 books today. In the 9 days prior to today, the same publishing company had produced an average (arithmetic mean) of x books per day. If today's record high increased average daily production to y books per day, what is x in terms of y?
a. (9y+180)/10
b. (10y+180)/9
c. (9y-180)/9
d. (10y-180)/9
e. 10y/9-180
Let x = 10 books per day.
Total number of books produced in the 9 days prior = 9*10 = 90.
y = average number of books produced over all 10 days = (180+90)/10 = 27.
The question asks for the value of x=10. This is our target.
Now we plug y=27 into the answers to see which yields our target of 10.
Only answer choice
D works:
(10*27-180)/9 = 90/9 = 10.
The correct answer is
D.
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