Circles geometry

Question

``The distance around a circular park is 2.8 mi. How many acres does it contain?

One square mile contains 640 acres.

Round the answer to the nearest integer.''.

Answer 1

Hi Sara,

Circumference of a circle, C = 2πr = 2.8 mi.

Solving for r = 2.8 mi./(2π) = .44563mi.

Then the area is A = π r² = .623 mi.²

Multiply by the conversion factor 640 acres/1 mi.²

.623 * 640 = 399 acres

 

Answer 2

circumference=pi*diameter

2.8=3.14159*d

2.8/3.14159=d

0.891268=d

r=0.891268/2=0.445634 mi

area=pi*radius²

A=3.14159*0.445634²

A=3.14159*0.198589

A=0.623885 sq mi

0.623885*640=399.2864 acres

to the nearest integer: 399 acres