
Elementary Math Fractions, Percentages, Word Problems, Equations, Inequations, Factorization, Expansion 
 LinkBack  Thread Tools  Display Modes 
October 2nd, 2011, 03:11 PM  #1 
Newbie Joined: Oct 2011 Posts: 1 Thanks: 0  Averages
I have a problem that I've been working on FOREVER! I CANNOT use Algebra or anything like Trig or Calculus to solve it. I have to describe it in it's basic form. By trial and error, I think the answer is 20, but I'm also not allowed to use trial and error (guess and check). How in the world can it be solved without Algebra? So far noone has been able to help me on other math forums without using Algebra. I already understand the Algebra way to solve it. Any ideas? 3. Two algebra classes took the same exam. The mean grade for the first class was 88. The second class had a mean grade of 79. The mean grade of the two classes combined was 84. If there were 25 students in the first class, how many were in the second class? 
October 2nd, 2011, 04:26 PM  #2 
Senior Member Joined: Jul 2010 From: St. Augustine, FL., U.S.A.'s oldest city Posts: 12,208 Thanks: 516 Math Focus: Calculus/ODEs  Re: Averages
We know the combined score for the first class is: Letting n be the number of students in the second class, their combined score is: The combined score of the two classes together is: We could also use a weighted average to state: The best way to solve this problem is to use algebra, representing the unknown quantity with a variable, then using given information to solve known relationships for that variable. 
October 3rd, 2011, 07:31 AM  #3  
Math Team Joined: Dec 2006 From: Lexington, MA Posts: 3,267 Thanks: 407  Re: Averages Hello, mswanson502! Quote:
I have many questions. Is this an assignment for a math class? [color=beige]. . [/color]If not, where did you find this problem? If so, at what level is the class? [color=beige]. . [/color]It appears to be at a preAlgebra level. [color=beige]. . [/color]Yet playingwithmeans seems quite advanced. Were you explicitly forbidden to use Algebra or guessing? [color=beige]. . [/color]Those are sadistic restrictions! I see no way so solve this without Algebra. [color=beige]. . [/color]MarkFL offered two excellent algebraic solutions. Without resorting to trialanderror, I have only one option: [color=beige]. . [/color]Pray ... and await Divine Inspiration.  

Tags 
averages 
Search tags for this page 
Click on a term to search for related topics.

Thread Tools  
Display Modes  

Similar Threads  
Thread  Thread Starter  Forum  Replies  Last Post 
Calculating averages  Leon22  Algebra  3  August 6th, 2013 06:41 PM 
Complexity of moving averages  mloone01  Computer Science  0  February 12th, 2011 12:29 PM 
weighted averages  stillrussian1  Advanced Statistics  0  September 27th, 2010 09:35 PM 
Figuring Out Averages  Cyberskull  Elementary Math  2  August 3rd, 2010 08:19 PM 
Question about averages and using a gradebook  LiamG  Academic Guidance  2  December 21st, 2009 12:10 AM 