Question

The inner circumference of a circular track is 330 m.The track is 10.5 m wide everywhere.Calculate the cost of putting up a fence along the outer circle at the rate of Rs.2 per metre.

Answer 1

Given
Circumference =330m
Width of track=10.5m

As we know circumference = 2 pi r

2 pi r=330

2x22/7 xr=330

R=330x7/44

=52.5m

Then Radius of outer circle = Radius of inner circle + width of track

=52.5+10.5=63m

Circumference of outer circle = 2 pi R

=2x22/7 x63

=2x22x9=396m

Cost of putting fencing on 1 m=₹2

Cost of putting fencing on 396m=₹792


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Answer 2

circumference = 2pi r

width = 10.5

circumference = 2 pi r

2 pi r = 330

2× 22/7×r = 330

R = 330 × 7/44

r = 52.5 meter

The radius of outer circle are = radius of inner circle + circle

+ width

= 52.5 + 10.5 = 63 meters

circumference of outer cycle

= 2 pi r

2 × 22 / 9 = 396

Cost of putting fencing 1m = ( rupee 2 per meter sq )

cost of fence on 396

so ( 396 × 2 )

= ( 792 ) is right answer ok