Ravi starts for his school at 8:20 a.m. on his bicycle. If he travels at a speed of 10 km/h. then he reaches his school late by 8 minutes but on travelling at 16 km/h he reaches the school 10 minutes early. At what time does the school start?
Let the total distance = x km
Let the time taken by Ravi to reach the school at sharp time = t min
If the speed of the bicycle is 10km/h, then he reaches his school late by 8 min
∴ 
⇒ 
(1)
If the speed of the bicycle is 16km/h, then he reaches his school 10min early.
∴ 
⇒ 
(2)
On subtracting equation (2) from (1)
⇒ 
⇒ 
⇒ 
⇒ 
Now, put x = 8 in Eq. (i),
we get 
⇒ 
Hence starting time of school is 8:20 + 40min i.e. 9:00am
90