Topic Details (Notes format)

How to Calculate Percentage Increase or Decrease

Subject: Mathematics

Book: Maths Mastery

Percentage changes are ubiquitous in daily life, from price hikes to interest rate drops. To calculate a percentage increase, use the formula: [(New Value – Original Value) ÷ Original Value] × 100%. For instance, if a product’s price rose from ₹200 to ₹240, the increase is (240 – 200) = 40, and dividing by 200 yields 0.20, or a 20% increase. Conversely, percentage decrease follows the same formula but indicates a reduction in value. For example, if a ₹300 item drops to ₹225, the change is (225 – 300) = –75, and –75 ÷ 300 = –0.25, or a 25% decrease. Understanding percentage changes enables you to track stock performances, budget effectively, and compare year-on-year business growth. Frequent practice in real scenarios like monthly bills or commodity prices refines this essential skill.

Practice Questions

The sum of the squares of two consecutive integers is 145. What are the integers?

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If the radius of a circle is doubled, what happens to its area?

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If x - y = 5 and x + y = 15, what is the value of x?

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What is the square root of 144?

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If 5x - 2 = 13, what is the value of x?

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If sin(A) = 1/2 and A is acute, what is the value of A?

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If the average of five consecutive odd numbers is 25, what is the largest number?

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If two complementary angles differ by 30°, what are the angles?

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If x² - 9x + 18 = 0, what are the roots of the equation?

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What is the square root of 121?

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