Question

Radha made a picture of an aeroplane with coloured paper as shown in Fig 12.15. Find the total area of the paper used.
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Answer 1

for surface 1

s=a+b+c/2

=5+5+1/2

=11/2cm

area of surface 1=√S (S-a)(S-b)(S-c)

=√11/2(11/2-5)(11/2-5)(11/2-1)

=√11/2×1/2×1/2×9/2

=3/4√11cm^

=(0.75×33)

=2.475cm^(approx)

for surface 2

it is a rectangle

area of surface 2: L×B

6.5×1

6.5cm^

it's height is given

=1/2[(sum of parallel sides)×h]

area of surface 3

=1/2×[(2+1)×√3/2]

3√3/4

3.1.732/4

1.3cm^(approx)

for surface 3

it's height is given by

h=√(1)^-(1/2)^

=√1-1/4

=√3/4

=√3/2cm

area of trapezium

=1/2[(sum of the parallel sides)×h]

area of surface 3

=1/2×[(2+1)×√3/2]

=3√3/4

=3×1.732/4

=1.3cm^(approx)

for surface 4 and 5

area of surface 4 = area of surface 5

1/2×b×h

1/2×6×15

4.5cm^

total are of paper used =(ar of surface 1)+(ar of surface 2)+(ar of surface 3)+(ar of surface 4)+(ar of surface 5)

=(2.475+6.5+1.3+4.5+4.5)

= 19.275

= 19.3cm^(approx)