11.3 Percentage change (MATH)

You can use percentages to describe a change in a quantity. It could be an increase or a decrease. 

A percentage change in always calculated a percentage of the initial value. 

The initial value is 100%. It is important to choose the correct value to be 100%.

Work this out:

• These are the masses of three children one April.

         Luke 6kg        Bridget 14kg        Tomas 25kg

         over a year, the mass of each of them increased by 10%. Work out the new mass of each children.

• "The price after the sale is $20 000 again"

      The price a car was $20 000. In a sale, the price decreased by 4%%.After the sale it increased by 4%.

      a. What mistake has Ahmad made?

      b. What is the correct price after the sale?

You may check this website if you still didn't understand: 

http://www.mathgoodies.com/lessons/percent/change.html

http://math.about.com/od/prealgebr1/a/percent.htm