Topic Details (Notes format)

How to Solve Proportions (Cross-Multiplication)

Subject: Mathematics

Book: Maths Mastery

Proportions equate two ratios, like a/b = c/d. Cross-multiplication states ad = bc. For example, if 2/5 = x/15, then 2 × 15 = 5 × x, meaning 30 = 5x, so x = 6. Proportions answer real-world questions: “If 2 liters costs ₹100, what does 5 liters cost?” or “If 3 out of 10 students prefer a subject, how many out of 50 might prefer it?” The technique is vital for scaling recipes, resizing images, or solving geometry similarity. Consistent practice ensures you can set up and solve ratio-based statements in a single, efficient step.

Practice Questions

What is the sum of all angles in a hexagon?

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A man spends 75% of his income and saves Rs. 600. What is his total income?

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

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The base of a triangle is 10 cm and its height is 6 cm. What is its area?

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What is the sum of the first 10 positive even numbers?

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

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The simple interest on Rs. 4000 at 5% per annum for 2 years is:

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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 x + 1/x = 5, what is the value of x^2 + 1/x^2?

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What is the area of a circle with a diameter of 14 cm?

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