The Math Forum

Ask Dr. Math - Questions and Answers from our Archives
Associated Topics || Dr. Math Home || Search Dr. Math

John's Losing His Marbles

Date: 8/26/96 at 11:29:16
From: Raymond
Subject: Losing Marbles

Dear Dr. Math,

Kindly advise the following :

John has twice as many green marbles as red marbles. When John lost 42 
green marbles, he had half as many green marbles as red marbles. How 
many marbles had he altogether at first?

I look forward to hearing from you soon. 

Thanks and best regards.

Date: 8/26/96 at 15:20:59
From: Doctor Robert
Subject: Re: Losing Marbles

Let x be the number of red marbles that John originally had.  Then, 
according to the problem, the original number of green marbles is 2x.  
Now when John lost 42 green marbles, he must have had 2x-42 green 
marbles.  According to the problem, this number is one half of the 
number of red marbles.  We can write the equation

     2x-42 = (1/2)x
   4x - 84 = x
        3x = 84
         x = 28.

So, he orginally had 28 red marbles and 56 green marbles for a total 
of 94 marbles.  Unfortunately, John is losing his marbles.

You can check to see whether the answer is correct.  If John loses 42 
green marbles he then has only 14 green marbles which is (1/2) of 28, 
the number of red marbles.  So, we know we're right.  That's what I 
like about word problems!

-Doctor Robert,  The Math Forum
 Check out our web site!   
Associated Topics:
Middle School Word Problems

Search the Dr. Math Library:

Find items containing (put spaces between keywords):
Click only once for faster results:

[ Choose "whole words" when searching for a word like age.]

all keywords, in any order at least one, that exact phrase
parts of words whole words

Submit your own question to Dr. Math

[Privacy Policy] [Terms of Use]

Math Forum Home || Math Library || Quick Reference || Math Forum Search

Ask Dr. MathTM
© 1994- The Math Forum at NCTM. All rights reserved.