The driver of an ambulance sees a school bus 40 m ahead of him after 20 seconds, the school bus is 60 meter behind. If the speed of the ambulance is 30 km/h, what is the speed of the school bus?
A. 10 kmph
B. 12 kmph
C. 15 kmph
D. 22 kmph
Answer: Option B
Solution (By Examveda Team)
Relative Speed, $$\eqalign{ & = \frac{{{\text{Total }}\,{\text{distance}}}}{{{\text{Total time}}}} \cr & = \frac{{60 + 40}}{{20}} \cr & = 5\,\,{\text{m/s}} \cr & = \frac{{5 \times 18}}{5} \cr & = 18\,\,{\text{kmph}} \cr} $$ Relative Speed = (speed of ambulance - speed of school bus) Speed of school bus = speed of ambulance - relative speed. = 30 - 18= 12 kmph.
This Question Belongs to Arithmetic Ability >> Speed Time And Distance
Where this 18 come from? Explain
x is the distance covered by the school bus between 40m and 60m
(60+40+x)/30*5/18= 20
x=200/3
speed of the School Bus=(200/3*20)*18/5=12
(60+40+x)/30*5/18= 20
x=(200/3*20)*18/5=12
How it comes 18