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

What is the LCM of 15 and 20?

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What is the sum of the first 20 odd numbers?

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The perimeter of a rectangle is 50 cm, and its length is 15 cm. What is its width?

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If the sides of a triangle are 6 cm, 8 cm, and 10 cm, what is the area of the triangle?

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A train 120 meters long is moving at a speed of 54 km/h. How long will it take to pass a pole?

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If the length of a rectangle is doubled and the width is halved, what is the change in area?

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If a cylinder has a radius of 7 cm and height of 10 cm, what is its volume?

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The perimeter of a rectangle is 40 cm, and its length is 12 cm. What is its width?

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The probability of rolling a sum of 7 with two dice is:

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If 2x - 3 = 7, what is the value of x?

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