Percetage Increase or Decrease


 
 
Concept Explanation
 

Percentage Increase or Decrease

Changes in quantities are often expressed as a percentage of the original quantity.

For Example :

  • Class sizes have increased by 10%.
  • House prices have dropped by 12%.
  • Carbon emissions need to fall by 25% by the year 2020.
  • To calculate the percentage increase:

  • First work out the difference (increase) between the two numbers you are comparing.
  • Increase = New Number - Original Number
  • Then divide the increase by the original number and multiply the answer by 100.
  • % increase = Increase ÷ Original Number × 100.
  • If your answer is a negative number, then this is a percentage decrease.
  • To calculate percentage decrease:

  • First find out the difference (decrease) between the two numbers you are comparing.
  • Decrease = Original Number - New Number
  • Then divide the decrease by the original number and multiply the answer by 100.
  • % Decrease = Decrease ÷ Original Number × 100
  • If your answer is a negative number, then this is a percentage increase.
  • There are two different methods which can be used to solve percentage increase or decrease problems.

    Method : Finding Percentage Increase or Decrease with two steps :

    Step 1 : Find the size of the increase or decrease.

    Step 2 : Apply the change to the original quantity by addition or subtraction.

    Example 1 :  A fruit grower picked 1720 kg of apples last year. This year she expects her crop to be 20% bigger. How many kilograms of apples does she expect to pick this year ?

    Step 1 : Size of increase =  20% of 1720 kg = 0.2 times 1720 kg = 344 kg

    Step 2 : New amount = 1720 + 344 kg = 2064 kg

    The fruit grower expects to pick 2064 kg.

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

    2.5 % increase in a salary of $ 1250 is ___________________

    Right Option : C
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    Explanation
    Question : 2

    The salary of a person goes up from Rs 100 to Rs 145. The percentage increase in his salary is ___________________ .

    Right Option : A
    View Explanation
    Explanation
    Question : 3

    A TV normally costs Rs 520. In a sale, all prices are reduced by 10% . Calculate the sale price of the TV

    Right Option : A
    View Explanation
    Explanation
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