Drexel dragonThe Math ForumDonate to the Math Forum

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

Pre-Algebra problem


Date: Fri, 11 Nov 1994 11:03:41 -0700 (MST)
From: John Murgel
Subject: pre-algebra

I am a teacher and would like to run this by you guys. Here is the 
problem: how would you go about helping a typical 7th grade 
student?

  -3n + 65 = -40 - 7n

My math count students will be working problems such as this in their 
state contest.


Date: Fri, 11 Nov 1994 16:55:59 -0500 (EST)
From: "Michael W. S. Morton"
Subject: Re: pre-algebra

Hey there!

        I'm one of the Math Doctors here.  I'll show you what I'd do to 
try to help out a 7th grader, and maybe some of the other math 
doctors have other ideas.

>   -3n + 65 = -40 - 7n

I may start with something like:

        n + 5 = 12

then ask what numbers would work there? (7).  Ask how the student 
came up with that answer.  Then explain it in this way:

        n + 5 = 12

subtract 5 from both sides of the equation:

        n + 5 - 5 = 12 -5
        n = 7

If subtracting a number from both sides of the equation is not clear 
to a student, try saying:

                        1 = 1
                does    1 - 5 = 1 - 5 ??

Since n represents a number ( a real, physical number) we can add 
or subtract a real number to both sides and not change anything.

So, moving on....

Then say:
        2n + 5 = 13
        2n + 5 - 5 = 13 - 5
        2n = 8
        n = 4

This should be relatively clear.
You can go from there...

As I'm typing this, I'm thinking this is not quite what you wanted to 
know (or wanted to hear)  If it is not, PLEASE write us back, and 
we'll try to help you out some more.  Sorry if this is over-simplified 
or not what you wanted; just write back and let us know!

                                        -MORTON, Doctor of sorts
    
Associated Topics:
Middle School Equations

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
© 1994-2013 The Math Forum
http://mathforum.org/dr.math/