Question

Fig. 12.27
13. A hand fan is made by stitching 10 equal size triangular strips of two different types of
paper as shown in Fig. 12.28. The dimensions of equal strips are 25 cm, 25 cm and 14 cm.
Find the area of each type of paper needed to make the hand fan.
Tf the sides of the​

Answer 1

Answer:

a=25cm,b=25cm,c=14cm

s=

2

a+b+c

=

2

25+25+14

=

2

64

=32cm

Area of one triangular strip =

s(s−a)(s−b)(s−c)

=

32(32−25)(32−25)(32−14)

=

32×7×7×18

=

16×2×7×7×3×3×2

=4×7×3×2

=168cm

2

Area of each types of paper needed

=5×168

=840cm

Answer 2

Let a = 25cm, b = 25cm, c = 14cm

s = a+b+c/2 = 25+25+14/2

= 64/2 = 32cm

Area = √s(s-a)(s-b)(s-c)

= √32*7*7*18

= √2*2*2*2*2*7*7*2*3*3

= 2*2*2*7*3

= 8*21

= 168cm²

Area of 1 triangular strip = 168cm²

Area of 5 traingular strips = 168*5 = 840cm²

⇒Area of 5 first type of strips = 840cm²

Area of 5 second type of strips = 840cm²