1. Semi circle word problem

2. To find : Cost of fencing Perimeter = r(π + 2) [ π = ,r = 35 ]
Example 1: Radius of a semicircle flower garden is 35m. What is the cost of fencing it at the cost of Rs.15 per metre.
Solution Given: Radius of the garden = 35m , Cost of fencing per metre = Rs.15
To find : Cost of fencing
Perimeter = r(π + 2)
[ π = ,r = 35 ]
= 5 x 36 = 180m
Cost of fencing for m = Rs.15
Cost of fencing for 180m = ?
Total cost = No.of metres x Cost for 1 metre
= 180 x 15 = Rs. 2700
Answer: Cost of fencing is Rs.2700
P = 180m 5
r = 35

3. To Find: Radius of the park Total cost = No.of metres x cost per metre
Example 2 : Cost of fencing a semicircular path at a rate of Rs.8 per metre is Rs What is the radius of the park ?
Solution: Given : Cost of fencing per metre = Rs.8 , Fencing cost = Rs.1152
To Find: Radius of the park
Total cost = No.of metres x cost per metre
= a x [let no.of metres be ‘a’]
Perimeter = r(π + 2)
r =4 x 7 = 28
Ans: Radius of the park is 28m.
P = 144m
r = 28 4 24 6

4. Try these
The radius of a semicircular hall is 21 m. What is the cost of fencing it at the cost of Rs.20 per metre ?
The cost of fencing a semicircular park at the rate of Rs.10 per metre is Rs What is the radius of the park.