The inside perimeter of a running track (showninFig.15.67) is 400m. The length of each of the straight portion is 90m and the ends are semi-circles. If the track is everywhere 14m wide, find the area of the track. Also find the length of the outer running track.
Answers
Answer:
6216 sq m
Step-by-step explanation:
Solution:-
The inside perimeter of the track = 400 m
The total length of the two straight portions = 90 + 90 = 180 m
Therefore the length of the remaining portion = 400 - 180 = 220 m
Circumference of the two remaining semi-circular portions = πr + πr = 2πr
'r' is the radius.
⇒ 2πr = 220
2 × 22/7 × r = 220
44r = 220 × 7
r = (220 × 7)/44
r = 35 m
So, the radius of the circular portion of the outer running running track = 35 m + 14 m = 49 m
Area of the track = Area of the two rectangles of dimensions 90 × 14 + The area of the circular rings.
= 2 × 90 × 14 + 22/7 × {(49)² - (35)²}
= 2520 + 22/7 ×(2401 - 1225)
= 2520 + (22 × 1176)/7
= 2520 + 25872/7
= 2520 + 3696
= 6216 sq m
Length of the outer running track = 2 × 90 + 2 × 22/7 × 49
= 180 + 308
Length of the outer running track = 488 m488 m
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