Question

Find the radius of a Circular 400m running track, taking π to be 22/7.

Answer Key - 63 7/11 m

Answer 1

Step-by-step explanation:

The inside perimeter of the track =400m

The total length of the two straight portions =90+90=180m

Therefore the length of the remaining portion =400−180=220m

Circumference of the two remaining semi-circular portions =πr+πr=2πr. ′r′ is radius

⇒  2πr=220

⇒  2×722×r=220

∴  r=35m

So, the radius of the circular portion of the outer running running track =35m+14m=49m

Area of the track = Area of the two rectangles of dimensions  + The area of the circular rings.

⇒  Area of track =2×90×14+722×[(49)2−(35)2]

⇒  Area of track =2520+722×(2401−1225)

⇒  Area of track =2520+722×1176

⇒  Area of track =2520+3696

∴  Area of track =6216m2

⇒  Length of the outer running track =2×90+2×722×49