Hushar Mulga
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In the given figure, BC ⊥ AB, AD ⊥ AB, BC = 4, AD = 8, then find (A(∆ABC))/(A(∆ADB))

Practice Set 1.1 | Q 2 | Page 6
In the given figure, BC ⊥ AB, AD ⊥ AB, BC = 4, AD = 8, then find (A(∆ABC))/(A(∆ADB))

practice set 1.2 similarity Fig 1.13
Solution

In ∆ABC and ∆ADB,
BC ⊥ AB, AD ⊥ AB, BC = 4, AD = 8   ...(Given)

∆ABC and ∆ADB have same base AB. ...(Given)

∴ Areas of triangles with equal bases are proportional to their corresponding heights.

(A(∆ABC))/(A(∆ADB)) = BC/AD

∴ (A(∆ABC))/(A(∆ADB)) = 4/8

∴ (A(∆ABC))/(A(∆ADB)) = 1/2.

Solution 2:- In the given figure, let’s denote the length of AB by ‘x’. Then, we can use the Pythagorean theorem to find the length of BC and AD:

BC² + AB² = AC² 4² + x² = AC² AC = sqrt(16 + x²)

AD² + AB² = BD² 8² + x² = BD² BD = sqrt(64 + x²)

Now, we can find the areas of triangles ABC and ADB:

A(∆ABC) = (1/2) * AB * BC = (1/2) * x * 4 = 2x

A(∆ADB) = (1/2) * AB * AD = (1/2) * x * 8 = 4x

Therefore, the ratio of the areas of the two triangles is:

A(∆ABC) / A(∆ADB) = (2x) / (4x) = 1/2

So, the ratio of the areas of triangles ABC and ADB is 1:2 or 1/2.

Chapter 1. Similarity- Practice Set 1.1  – Page 5

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