Percentage Change


 
 
Concept Explanation
 

Percentage Change

Percentage Change: is calculated by dividing the change with original and multiplying with 100

small small Percentage;Change = frac{ Change}{Original} X 100

Here are two ways to calculate a percentage change, use the one you prefer:

Method 1:

Step 1: Calculate the change (subtract old value from the new value)
Step 2: Divide that change by the old value (you will get a decimal number)
Step 3: Convert that to a percentage (by multiplying by 100 and adding a "%" sign)
 
Note: when the new value is greater then the old value, it is a percentage increase, otherwise it is a decrease.

Method 2:

Step 1: Divide the New Value by the Old Value (you will get a decimal number)
Step 2: Convert that to a percentage (by multiplying by 100 and adding a "%" sign)
Step 3: Subtract 100% from that
 
Note: when the result is positive it is a percentage increase, if negative, just remove the minus sign and call it a decrease.

ILLUSTRATION: A pair of socks went from Rs 5 to Rs 6, what is the percentage change?

Answer (Method 1):

  • Step 1: Amount has changed from Rs 5 to Rs 6. There is an increase of Re 1
  • Step 2: Divide by the old value: 1/5 = 0.2
  • Step 3: Convert 0.2 to percentage: 0.2×100 = 20% rise.
  • Answer (Method 2):

  • Step 1: Divide new value by old value: 6/5 = 1.2
  • Step 2: Convert to percentage: 1.2×100 = 120% (i.e. Rs 6 is 120% of Rs 5)
  • Step 3: Subtract 100%: 120% - 100% = 20%, and that means a 20% rise.
  • ILLUSTRATION: Population in a country in the year 2010 was 99000 and in 2009 it was 90000. Find the percentage change.

    Sol :   Population in 2009 = 90000.

              Population in 2010 = 99000.

              Change = 99000 - 90000 = 9000

            small small Percentage;Change = frac{ Change}{Original} X 100

          small Percentage;Change = frac{ 9000}{90000} X 100 = 10%

    Sample Questions
    (More Questions for each concept available in Login)
    Question : 1

    A towel was 50cm broad and 100cm long.when bleached it was found to have lost 20% if is length and 10% of its width.the percentage of decreases in area is

    Right Option : A
    View Explanation
    Explanation
    Question : 2

    If redius of a circle is increased by 100% then area of the circle will be increased by

    Right Option : C
    View Explanation
    Explanation
    Question : 3

    If radius of a circle is increased by 50% then area of the circle will be increased by

    Right Option : C
    View Explanation
    Explanation
     
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