Is the Calculator '%' Button Really Magic?
Throughout our day we are regularly in situations where we must calculate a percentage of something and I worry when I watch someone struggle with this task simply because they can't find the percent key on their calculator. Have we become so reliant on our technology that we cannot remember the basic mathematical operations we were taught in school?
As thousands of school students sit in class learning how to recognise and calculate percentages, I wonder how many of them really understand that the calculator percent button does no more than
divide by 100!
Recently I was tutoring a 15 year old student who began desperately searching for the percent key on his new scientific calculator. To his horror, the calculator did not provide this function, and so began a half hour lesson on dealing with calculating percentages without the percent key.
Let's look at an example:
Suppose I was being offered a 22% discount on a television selling for $800. What is the amount of my discount, and how much would I actually be paying?
To answer this question we must first find the amount of the discount which is 22% of $800.
The word 'of' in mathematics means 'multiply'.
Replace 'of' with 'multiply'.
The '%' sign means 'divide by 100'.
Replace '%' with 'divide by 100'.
Now calculate the answer from left to right.
So we will be given a discount of $176 on our television set. Let's calculate our final price.
Take our $176 discount from the $800 price.
We are only going to pay $624 for the television that normally sells for $800.
Remember '%' means divide by 100.
