The area of the square field is 900metre square . How much times will a girl take to run 10 times around it at the rate of 6kmper hour
Answers
12 minutes.
Explanation:
It is stated that,
The area of the square field is 900 m².
Area = (side)²
= (side×side)
∴Side = √(area)
⇒ Side = √(900)
= 30 m.
∴ The length of the side of the field is 30 m.
Perimeter =(4×side)
=(4×30) m
= 120 m.
∴ The perimeter of the field is 120 m.
The distance covered by the girl by running 1 time around the field = The perimeter of the field = 120 m.
Hence,
In 1 time the girl covers a distance of 120 m.
∴ In 10 times the girl covers a distance of (120×10) m
= 1200 m.
The speed of the girl is 6 km/h.
The speed of the girl in m/s = (6*5/18)
= (5/3) m/s
Hence,
(5/3) m is covered by the girl in 1 second.
∴ 1 m is covered by the girl in (3/5) second
∴ 1200 m is covered by the girl in (3×1200/5)
= (3×240)
= 720 seconds
= (720÷60) minutes [∵1 minute= 60 seconds]
= 12 minutes.
∴ The girl will take 12 minutes to run 10 times around he field.