How long will a boy take …

First, we need to convert the boy's speed from kilometers per hour (km/hr) to meters per second (m/s), which is the standard unit of speed for measuring distances in meters. To do this, we can use the conversion factor 1 km/hr = 1000 m/3600 s. 9 km/hr = (9 * 1000) / 3600 m/s ≈ 2.5 m/s (rounded to one decimal place) The distance around the square field is the perimeter, which is four times the length of one side: Perimeter = 4 × side length = 4 × 35 m = 140 m The time it takes the boy to run around the field is the distance divided by his speed: Time = Distance / Speed = 140 m / 2.5 m/s = 56 s Therefore, the boy will take 56 seconds to run around the square field of side 35 meters at a speed of 9 km/hr.