Percent of Change 6-8
% OF INCREASE OR DECREASE:
You compute these the same way, only one is an increase and the other is a decrease
% of increase or decrease =
Increase or decrease
Original amount
HOW DO YOU FIND THE INCREASE OR DECREASE FOR THE NUMERATOR?
Think about it!
If you had $10 and now you have $15, how much did your money change?
$5
Was it an increase or decrease?
Increase!
You had a 98 in the class and now you have a 92.
How much did your grade change?
6 points
Was it an increase or decrease?
Decrease!
SO HOW DO YOU FIND THE INCREASE OR DECREASE FOR THE NUMERATOR?
SUBTRACT!
NOTICE THAT THE DENOMINATOR IS ALWAYS THE ORIGINAL
WHY?
You want to know what your number CHANGED FROM
EXAMPLE:
Original grade = 80 and new grade = 90
for an increase of 10 points
% of increase =
10/80 = 1/8 = .125
= 12.5%
EXAMPLE:
Original grade = 90 and new grade = 80
for a decrease of 10 points
% of decrease = 10/90 = 1/9 = .111. . . or about 11%
WHY ARE THE %s DIFFERENT WHEN THE CHANGES ARE THE SAME (10 points)?
The Percent of Change is based on WHAT YOU STARTED WITH.
In the first case, the original grade was 80, but in the second example, the original grade was 90.
10 points is a bigger percent of 80 than it is of 90!
STILL DON'T GET THAT?
LET'S DO AN EXAMPLE THAT IS VERY DIFFERENT!
Original grade: 20 (yes, I said 20% in the class :(
New grade: 30
Increase: 30 - 20 = 10
What did it increase from? 20
%
PERCENT OF INCREASE: 10/20 = 50%
INCREASE!!!!
Now I know this student is still failing, but he(she) has increased the grade 50% of the prior grade!
FROM THE ABOVE EXAMPLE, YOU CAN SEE HOW PERCENT OF CHANGE CAN BE MISUSED BY PEOPLE LIKE ADVERTISERS!
The student above can tell his parents: "I increased my grade 50%!!!
"
That's true! But his parents should immediately say 50% increase FROM WHAT?
An advertisement says: Your teeth will be 50% whiter!
50% whiter FROM WHAT?
You will get 50% better gas mileage if you use our gas.
50% better than what?
Subscribe to:
Post Comments (Atom)
No comments:
Post a Comment