# Cost Efficiency Of Two Computers!

### By: Smita, Period 1 #25

## Situation

They have two options between two models :

- Computer A costs $700 (but uses 0.143 kilowatts/hour); which will cost about $42.00 each year. (0.143*8*365*0.1=$42)

- Computer B costs $550 (but uses 0.246 kilowatts /hour); which will cost about $72.00 each year. (0.236*8*365*0.1=$72)

The school wants to buy a long term computer which will last at least 10 years.

Which computer should the School purchase based on the cost efficiency of the computers?

## The Classification Of The Variables

The two variables are the number of years and the cost.

Number Of Years is the independent variable and will be represented using the variable yThe Cost is the dependent variable and will be represented by using the variable C

## Table Of Values

## Equations:

## In y=mx+b Form

* m*: (slope) the yearly cost

__b__: (y-intercept) initial cost of the computer

__y__:(dependent variable)total cost; represented by the variable **C**

__x__:(independent variable)number of years; represented by the variable **y**

Computer B: C=72y+550

(Both equations represent partial variation)

## Graph

## P.O.I. & The Significance Of the Data

__Point of Intersection is (5, 910)__The point of intersection satisfies both equations:

Computer A:

C=42y+700

(Substitute value of C and y)

910=42(5)+700

=910=210+700

=910=910

Computer B:

C=72y+550

(Substitute value of C and y)

910=72(5)+550

=910=360+550

=910=910

The significance of the Point Of Intersection in this situation is that both computers will cost the same at the same point in time. Thus in 5 years both computers will cost $910.

__Significance Of The Data:__

- If the school uses the computer for 5 years it would cost both Computer A and Computer B $910.
- If the school is planning to use the computer for less than 5 years it would be inexpensive to purchase Computer B.
- Although, if the school is planning to use the computer for more than 5 years it would be inexpensive to choose Computer A.