If Sohail walks from his home to office at 16 km/h, he is

If Sohail walks from his home to office at 16 km/h, he is late by 5 min. If he walks at 20 km/h, he reaches 10 min before the office time. Find the distance of his office from his house.

Let required distance = L
According to the question,
L/16 - L/20 = 15/20
⇒ (5L - 4L)/80 = 1/4
∴ L = (1/4) x 80 = 20 km