Q&A for How to Calculate Percent Change

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  • Question
    What is the percent of change from 1/4 to 1/2?
    Community Answer
    Say you were asked to find the change from 0.25 to 0.5, you would say that it got doubled. In percentage form, this equates to 100%.
  • Question
    How do I calculate percent change when the original number is zero?
    Donagan
    Top Answerer
    That is an "undefined" situation, because any percentage of zero is zero.
  • Question
    How do I calculate percent change when $40 becomes $30?
    Community Answer
    First find the difference by subtracting. 40 - 30 = 10. Then divide the result by the original number. 10/40 = 0.25. Then multiply by 100. 0.25 x 100 = 25%.
  • Question
    I watched a video that stated the timing of 50ms went down to 20ms. He reported that as 205% improvement. How is that calculated?
    Donagan
    Top Answerer
    It was calculated incorrectly. It's an improvement of 60%.
  • Question
    If the original quantity is 6 and the new quantity is 3, what is the percent decrease?
    Donagan
    Top Answerer
    The percent change is -50%.
  • Question
    Lets say I bought 1360 jeans last year. This number increased by 5% this year. How many jeans did I buy this year?
    Donagan
    Top Answerer
    1,360 + (.05)(1,360) = 1,360 + 68 = 1,428.
  • Question
    How do I find a percent change if the denomenator is not a factor of 100?
    Donagan
    Top Answerer
    The process remains the same: divide denominator into numerator. You'll get a decimal number. Multiply by 100, and add a percent sign.
  • Question
    By what percent will the product of two numbers decrease if one of them is increased by 30% and the other is decreased by 30%?
    Community Answer
    It will decrease by 0.09%. 30% is the same as 0.3. When 0.3 is multiplied with 0.3, the result is 0.09. Let's say both numbers are 10. If one of them increases to 13 and the other decreases to 7, the product would be 91. Compared to 100, 91 has a 0.09% decrease. Now if the two numbers were 10 and 20, let's say 10 increased to 13 and 20 decreased to 14. The product of 13 and 14 would be 182. When compared to 200, 182 also has a 0.09% decrease.
  • Question
    How can I find out a percent change?
    Community Answer
    If the number is a decimal, multiply the number by 100. If it is a fraction, divide the numerator by the denominator and then multiply by 100.
  • Question
    I have been asked to provide week-over-week (WoW) numbers at work. Is this calculation what they would be asking for?
    Donagan
    Top Answerer
    Only "they" know for sure what they're asking for, but week-over-week customarily involves real-number changes or percentage changes from week to week. So yes, they may indeed be looking for what this article demonstrates.
  • Question
    By what percent will the product of two numbers change if the first number increases by 70%, while the second number decreases by 40%?
    Donagan
    Top Answerer
    The first number is multiplied by 1.7 (an increase of 70%). The second number is multiplied by 0.6 (which is a decrease of 40%). The final product is 1.7, multiplied by 0.6, multiplied by the original product. That means the final product is 1.02 times the original product.
  • Question
    New value and percentage change is given; how do I find the old value, given that the formula is (new-old)/old = % change?
    Donagan
    Top Answerer
    Divide the new price by the sum of 1 plus the % change. For example, if the new price is 100, and the percentage of change is +10%, the old price is 100 / (1 + 10%) which is 100 / (1 + .1) or 100 / 1.1. That equals 90.91, the old price. To check the answer: 90.91 + 10% of 90.91 = 90.91 + 9.09 = 100.
  • Question
    a) The price of a commodity decreased by 20% between 2015 and 2017 and increased by 25% between year 2017 and 2020. Using the price relative concepts, find the percentage change in price?
    John Sanders
    Community Answer
    (0.8)(1.25) = 1, the price of a commodity remains stable. The total percentage change is equal to 0.
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