A student walks from his house at 2½ km/h and reaches his school late by 6 min. Next day, he increases his speed by 1.2 km/h and reaches 6 min before school time. How far is the school from his house?
Answer & explanation
Correct answer: option 1
Let the student take ‘x’ hours to reach at his normal speed.
When the student walks at 2.5 km/hr,
He reaches in (x + 6/60) hours
∴ Distance = 2.5 × (x + 0.1) ----(1)
When the student walks at 3.7 km/hr,
He reaches in (x - 6/60) hours
∴ Distance = 3.7 × (x - 0.1) ----(2)
From (1) and (2) we get,
∴ 2.5 (x + 0.1) = 3.7(x - 0.1)
∴ 2.5x + 0.25 = 3.7x - 0.37
∴ x = 0.517 hours
∴ From (1) we get
⇒ Distance = 2.5 × (0.517 + 0.1) ≈ 1.5 km