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Tuesday, November 8, 2011

Nils' Textbook Question

Chapter 2.2
Problem Solving with Rational Numbers in Decimal Form
Question #27
The mean of six rational numbers is -4.3
a) What is the sum of the rational numbers?
b) If five of the numbers each equal -4.5, what is the sixth number?

First of when looking at the question the first thing that pops into some people's minds is, what is a mean? A mean is a way of calculating the average of a set of numbers by adding all the numbers together and diving by the amount of numbers in the set.

For a) we would first think how the mean is -4.3.
We know that x/6 = -4.3
X is the sum of the rational numbers.
In order to find that sum I used reverse operations to isolate x.
x/6 X 6 = -4.3 X 6
x = -25.8
The sum of the rational numbers is -25.8.

For b) I like to write it down using algebra.
[(-4.5) + (-4.5) + (-4.5) + (-4.5) + (-4.5)] + x = -25.8
Here 5 out of the six numbers are -4.5 just like the question says.
When added the numbers are...
(-22.5) + x = -25.8
I like to isolate the x by using the reverse operation.
(-22.5) - (-22.5) + x = -25.8 - (-22.5)
x = -3.3
The sixth number is -3.3.

If you have any questions concerning this post or anything about chapter 2, feel free to ask me or if I don't know go see Mr. Backe in the morning.


  1. Good post Nils ! You really explained how you answered the question well. But maybe a few pictures would make it easier to read because "/" can get people confused if it is a fraction or not.

  2. Good job Nils! I liked how you explained how to find the answer, it was really easy to understand. But you could have added some color or made some key words bold. Anyways good job!!!