In a certain class, $x$ students are $10$ years old, and the remaining $y$ students are $11$ years old. What is

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Vincen: Legendary Member; Posts: 2898; Joined: Thu Sep 07, 2017 2:49 pmFollowed by: 5 members; Thanked: 6 times

by Vincen » Mon Oct 19, 2020 9:30 am

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In a certain class, $x$ students are $10$ years old, and the remaining $y$ students are $11$ years old. What is the average (arithmetic mean) age of all students in the class?

A. $\dfrac{x+y}{21}$

B. $\dfrac{10x+11y}{21}$

C. $\dfrac{110xy}{x+y}$

D. $\dfrac{110xy}{xy}$

E. $\dfrac{10x+11y}{x+y}$

Answer: E

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Re: In a certain class, $x$ students are $10$ years old, and the remaining $y$ students are $11$ years old. What

by Scott@TargetTestPrep » Tue Oct 27, 2020 10:02 am

Vincen wrote: ↑
Mon Oct 19, 2020 9:30 am
In a certain class, $x$ students are $10$ years old, and the remaining $y$ students are $11$ years old. What is the average (arithmetic mean) age of all students in the class?

A. $\dfrac{x+y}{21}$

B. $\dfrac{10x+11y}{21}$

C. $\dfrac{110xy}{x+y}$

D. $\dfrac{110xy}{xy}$

E. $\dfrac{10x+11y}{x+y}$

Answer: E

Solution:

The sum of the ages of x students is 10x years old, and the sum of the ages of y students is 11y years old. Since there is a total of x + y students, the average age is (10x + 11y) / (x + y) years old.

Answer: E

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