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# The Perimeter of a Triangular Field is 240 Dm. If Two of Its Sides Are 78 Dm and 50 Dm, Find the Length of the Perpendicular on the Side of Length 50 Dm from the Opposite Vertex. - Mathematics

The perimeter of a triangular field is 240 dm. If two of its sides are 78 dm and 50 dm, find the length of the perpendicular on the side of length 50 dm from the opposite vertex.

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#### Solution

ABC be the triangle, Here a = 78 dm = AB,
BC = b = 50 dm

Now, perimeter = 240 dm
⇒ AB + BC + CA = 240 dm
⇒ AC = 240 – BC – AB
⇒ AC = 112 dm
Now, 2s = AB + BC + CA
⇒ 2s = 240
⇒ s = 120 dm

∴ Area of ΔABC =sqrt(s(s-a)(s-b)(s-b)) by heron's formula

=sqrt(120(120-78)(120-50)(120-112))

=sqrt(120xx42xx70xx8)

1680 dm^2

𝐿𝑒𝑡 𝐴𝐷 𝑏𝑒 𝑝𝑒𝑟𝑝𝑒𝑛𝑑𝑖𝑐𝑢𝑎𝑙𝑎𝑟 𝑜𝑛 𝐵𝐶

Area of ΔABC = 1/2xx ABxxBC (area of triangle=(1/2xxbxxh)

=1/2xx ADxxBC=1680

⇒AD=(2xx1680)/50=67.2dm

Concept: Area of a Triangle by Heron's Formula
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#### APPEARS IN

RD Sharma Mathematics for Class 9
Chapter 17 Heron’s Formula
Exercise 17.1 | Q 7 | Page 8
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