Find the perimeter of the lawn. Rani bought a new field that is next to one she already owns (Fig. 9.34). This field is in the shape of a square of 70 m. She makes a semi circular lawn of maximum area in this field.
Solution:
Given, Rani bought a new field that is next to one she already owns.
The new field is in the shape of a square of 70 m.
She makes a semicircular lawn of maximum area in this field.
We have to find the perimeter of the lawn.
For maximum area, the side of the square will be the diameter of a semicircle.
Diameter = 70 m
Radius, r = 70/2 = 35 m
Perimeter of semicircular lawn = 2πr/2 + 2r
=πr + 2r
= r(π+2)
= 35 (22/7 + 2)
= 35 [(22+14)/7]
= 35 (36/7)
= 5(36)
= 180 m
Therefore, the perimeter of the lawn is 180 m.
✦ Try This: Pavi bought a new field that is next to one she already owns. This field is in the shape of a square of 100 m. She makes a semi circular lawn of maximum area in this field. Find the perimeter of the lawn.
☛ Also Check: NCERT Solutions for Class 7 Maths Chapter 11
NCERT Exemplar Class 7 Maths Chapter 9 Problem 80(i)
Find the perimeter of the lawn. Rani bought a new field that is next to one she already owns (Fig. 9.34). This field is in the shape of a square of 70 m. She makes a semi circular lawn of maximum area in this field.
Summary:
Rani bought a new field that is next to one she already owns (Fig. 9.34). This field is in the shape of a square of 70 m. She makes a semi circular lawn of maximum area in this field. The perimeter of the lawn is 180 m
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