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 Apr 22, 2020
 #1
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First one,

"The perimeter of the triangle is 30" 

Perimeter is the sum of outer lines of a shape. 

(The three sides of this triangle)

so, 3a=30 thus a=10 cm

Rectangle's perimeter = 2(l+w)=2l+2w , given l=a and w=b then

2a+2b=30 

Since a=10 

20+2b=30 , 2b=10 , b=5

Area of square is side squared.

b is the side so \(b^2=5^2=25\) \(cm^2\)

 Apr 22, 2020
 #2
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Second one, 

Draw a line from B to D 

Notice it is two right-angled triangles.

area of triangle \(\frac{1}{2}*b*h\) (b=base, h=height)

so

Area of the first triangle: \(\frac{1}{2}*18*7.5=67.5cm^2\)

Area of the second triangle: \(\frac{1}{2}*15.6*11.7=91.26cm^2\)

Thus area of the quadrilateral is the sum of both

\(67.5+91.26=158.76cm^2\)

 Apr 22, 2020

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