A runner tracks a circular field of radius 140 meters. If his speed is 5 m/s, how long does he take to complete a single lap? MCQ with Answer and Explanation

Explanation:
Total distance = 140 + 260 = 400 meters. Speed = 400 / 20 = 20 m/s. In km/h = 20 * (18/5) = 72 km/h.

Explanation:
Speed of train = 54 * (5/18) = 15 m/s. Length of train layout = Speed * Time = 15 * 10 = 150 meters.

Explanation:
Let original speed be s. 360/s - 360/(s+10) = 3. Dividing by 3: 120/s - 120/(s+10) = 1. 120(s + 10 - s) = s(s + 10) => 1200 = s(s + 10). Solving s^2 + 10s - 1200 = 0 gives (s-30)(s+40) = 0. Since speed is positive, s = 30 km/h.