Amrita travels from her house at 3½ km/h and reaches her school 6 minutes late. The next day she travels at 4½ km/h and reaches her school 10 minutes early. What is the distance between her house and the school?
Show answer & explanation
Correct answer: D
Explanation
The correct answer is option 4 i.e. 4.2 km
Let the usual time to reach at school in t minutes.
Distance = time × speed.
In the first case, Amrita travels from her house at 3½ km/h and reaches her school 6 minutes late
Distance = (t + 6) × 7/2............(1)
In the second case, she travels at 4½ km/h and reaches her school 10 minutes early.
Distance = (t - 10) × 9/2...........(2)
On combining 1 and 2 we get,
7t/2 + 21 = 9t/2 - 45
t = 66 minutes.
Distance = (t + 6) × 7/2.
= 72/60 × 7/2 = 4.2 km.