Starting from his house, one day a student walks at a speed

Starting from his house, one day a student walks at a speed of 3 km/h and reaches his school 5 min late. Next day he increases his speed by 1 km/h and reaches the school 3 min early. How far is the school from his house ?

Let the distance be D km
Difference in timings = 8 min = 8/60 h = 2/15 h
∴ D/3 - D/4 = 2/15
⇒ D/12 = 2/15
⇒ D = 2 x 12/15 = 1.6 km