An ant is moving around a few food pieces of different shapes scattered on the floor. For which food-piece would the ant have to take a longer round? Remember, circumference of a circle can be obtained by using the expression c=2πr where r is the radius of the circle.

(a) Radius = Diameter/2 = 2.8/2 = 1.4 cm
Circumference of semi circle = πr=22/7×1.4=4.4 cm
Total distance covered by the ant = Circumference of semi circle + Diameter
= 4.4 + 2.8 = 7.2 cm

(b) Diameter of semi circle = 2.8 cm
∴ Radius = Diameter/2 = 2.8/2 = 1.4 cm
Circumference of semi circle = πr=22/7×1.4=4.4 cm
Total distance covered by the ant = 1.5 + 2.8 + 1.5 + 4.4 = 10.2 cm

(c) Diameter of semi circle = 2.8 cm
∴ Radius = Diameter/2 = 2.8/2 = 1.4 cm
Circumference of semi circle = πr=22/7×1.4=4.4 cm

Total distance covered by the ant = 2 + 2 + 4.4 = 8.4 cm
Hence for figure (b) food piece, the ant would take a longer round.

Class 8 Maths Chapter 11 Exercise 11.1 Solution in Video

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