Question

The diameter of a circular park is 84m.On its outside,there a3.5m wide road.Find the cost of constructingthe road at₹240 per m²

Answer 1

Heya...
Here is your answer ----

Larger circle = Circle B
Smaller circle = Circle A

=> Radius of Circle A = Diameter ÷ 2 = 84 ÷ 2 = 42 m

=> Area of Circle A = π × r^2

=> Area of Circle A = 22/7 × 42^2

=> Area of Circle A = 22/7 × 1764

=> Area of Circle A = 22 × 252

=> Area of Circle A = 5544 m^2

_______________________

=> Radius of Circle B = 42 + 3.5 = 45.5 m

=> Area of Circle B = π × r^2

=> Area of Circle B = 22/7 × (45.5)^2

=> Area of Circle B = 22/7 × 2070.25

=> Area of Circle B = 22 × 295.75

=> Area of Circle B = 6506.5 m^2

______________________

=> Area of road = Area of Circle B - Area of Circle A

=> Area of road = 6506.5 - 5544

=> Area of road = 962.5 m^2

______________________

=> Cost of constructing = Area × Cost/m

=> Cost of constructing = 962.5 × 240

=> Cost of constructing = ₹ 2,31,000
______________________

HOPE IT HELPS.....!!!!

Answer 2

heya!!

here is your solution -

Larger circle = Circle B
Smaller circle = Circle A

Radius of Circle A = d ÷ 2 = 84 ÷ 2 = 42 m

Area of Circle A
= π × r²
= 22/7 × 42²
= 22/7 × 1764
= 22 × 252
= 5544 m²

=> Radius of Circle B = 42 + 3.5 = 45.5 m

Area of Circle B
= π × r²
= 22/7 × 45.5²
= 22/7 × 2070.25
= 22 × 295.75
= 6506.5 m²

Area of road
= Area of Circle B - Area of Circle A
= 6506.5 - 5544
= 962.5 m²

Cost of constructing
= Area × Cost/m
= 962.5 × 240
= ₹ 2,31,000

hope it helps!!