# Cost Efficiency Of Two Computers!

## Situation

A school is deciding to buy a long term cost efficient computer for it's office. The school is planning to use the computer for 8 hours each day. (The cost of electricity is \$0.1/kwh).

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 y

The Cost is the dependent variable and will be represented by using the variable C

## 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 A: C=42y+700

Computer B: C=72y+550

(Both equations represent partial variation)

## 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.

## Conclusion:

Therefore, the school should purchase Computer A because they want a computer to use for at least 10 years and in 10 years Computer A is more cost efficient than Computer B!