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 sum of the interior angles of a hexagon?

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A number is increased by 20% and then decreased by 20%. What is the net change?

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The sides of a triangle are 13 cm, 14 cm, and 15 cm. What is its area?

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If sin(θ) = 0.6 and θ is acute, what is cos(θ)?

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If a cone has a base radius of 3 cm and height of 4 cm, what is its slant height?

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If the angles of a triangle are in the ratio 2:3:4, what is the measure of the largest angle?

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

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If a:b = 7:9 and b:c = 5:6, what is a:c?

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What is the square root of 144?

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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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