Correct Answer - Option 2 : 5 km
Given
Ram speed 4 km per hr. reached at school 9 minutes late
ram speed 5 km per hr. reached at school 6 minutes earlier
Let the required distance be x kms.
When speed is 4 km per hr., time taken t1 = x/4 hours
Again, when speed is 5 km per hr, time taken t2 = x/5 hours
Difference in timings = 9 + 6 = 15 minutes = 15/60 hours
Calculation
t1 − t2 = 15/60
t1 − t2 = 1/4 hrs
∴ x/4 − x/5 = 1/4
⇒ (5x−4x)/20 = 1/4
⇒ x/20 = 1/ 4
⇒ x = 20/4
∴ x = 5 kms
Hence required answer distance = 5 kms