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Find the area of a triangle two sides of which are 18cm and 10cm and the perimeter is 42cm.

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Given, Side a=18cm, Side b=10cm, Perimeter=42cm=a+b+c :. Putting value 42=18+10+c 42=28+c 42-28=c 14=c Now,S=(a+b+c)/2 :. Putting value S=42/2S=21 Now according to Heron's formula Area of a triangle=√{s(s-a)(s-b)(s-c)} :....
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Given,
Side a=18cm, Side b=10cm, Perimeter=42cm=a+b+c
:. Putting value 42=18+10+c
                       42=28+c
                       42-28=c
                       14=c
Now,S=(a+b+c)/2
:. Putting value S=42/2S=21
Now according to Heron's formula
Area of a triangle=√{s(s-a)(s-b)(s-c)}
:.    Putting value=√{21(21-18)(21-10)(21-14)}
                         =√{21(3)(11)(7)}
                         =√4851=21√11cm²
 
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Maths Teacher for classes 6th to 10th with 6 years experience and having my own YouTube Channel for clearing doubts

Perimeter of a triangle is the sum of all the three sides of that triangle. So, the third side of the triangle = 42cm - (18cm + 10cm) = 42cm - 28cm = 14cm. So, the three sides of the triangle are 18cm, 10cm and 14cm. Area of the triangle, using Heron's Formula is 69.65cm².
Comments

Let the third side be c. ∴ 18cm + 10cm + c = 42cm ∴ c = 42cm - 28cm = 14cm. ∴ the area of the triangle = √21 ( 21 - 10 ) ( 21 - 14 ) ( 21 - 18 ) = √21 × 11 × 7 × 3 = 21√11cm².
Comments

Given,Side a=18cmSide b=10cmPerimeter=42cm=a+b+c:. Putting value42=18+10+c42=28+c42-28=c14=cNow,S=(a+b+c)/2:. Putting valueS=42/2S=21Now according to Heron's formula-Area of a triangle=√{s(s-a)(s-b)(s-c)}:. Putting value=√{21(21-18)(21-10)(21-14)}=√{21(3)(11)(7)}=√4851=21&radi...
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Given,
Side a=18cm
Side b=10cm
Perimeter=42cm=a+b+c
:. Putting value
42=18+10+c
42=28+c
42-28=c
14=c
Now,
S=(a+b+c)/2
:. Putting value
S=42/2
S=21
Now according to Heron's formula-
Area of a triangle
=√{s(s-a)(s-b)(s-c)}
:. Putting value
=√{21(21-18)(21-10)(21-14)}
=√{21(3)(11)(7)}
=√4851
=21√11cm²

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Comments

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