Walking at 6/7 of his typical speed, a clerk reaches his documentation terminal 14 minutes late. What is his typical time? MCQ with Answer and Explanation

Explanation:
Let original speed be s. 450/(s-15) - 450/s = 1.5 => 300/(s-15) - 300/s = 1 => 300(15) = s(s-15) => 4500 = s(s-15). Solving s^2 - 15s - 4500 = 0 gives (s-75)(s+60) = 0. Baseline speed = 75 km/h.

Explanation:
Time difference = 6 - (-6) = 12 minutes = 12/60 = 1/5 hour. Let distance be d. d/4 - d/5 = 1/5 => d/20 = 1/5 => d = 4 km.

Explanation:
Total distance = 60 + 100 = 160 km. Time for first leg = 60 / 30 = 2 hours. Time for second leg = 100 / 50 = 2 hours. Total time = 4 hours. Average speed = 160 / 4 = 40 km/h.