A starts from a place at a constant speed of 5 km/hr in a particular direction. After an hour B starts from the same place and over takes A after two and half hours. Calculate the speed of B?
Answers
Answer:
Let the speed of A is x km/hr and speed of B is y km/hr
Let them meet after t hours Then xT+yT= Total distance
After the meeting distance left for A=yT and the distance left for B=xT Now yT=4x and xT=9y
∴
xT
yT
=
9y
4x
⇒
y
2
x
2
=
4
9
⇒
y
x
=
2
3
⇒x:y=3:2
Given,
A has a constant speed of = 5 km/hr
B starts journey after one hour, and over takes A after 2.5 hours.
To find,
The speed of B.
Solution,
We can simply solve this mathematical problem by using the following mathematical process.
Now, as per the data mentioned in the question.
Travelling time of B = 2.5 hours
Travelling time of A = Travelling time of B + Inital 1 hour when only A was travelling = (2.5+1) = 3.5 hours
So, distance travelled by A :
= Speed × Total time
= 5 × 3.5
= 17.5 km
Now, for B to overtake A, B has to cover the distance which is equal to the distance covered by A.
So, speed of B
= Distance travelled by B / Travelling time of B
= 17.5/2.5
= 7 km/hr
(With this speed, the B will catch up A in 2.5 hours even after starting the journey 1 hour late than A. Now, after catching up A in 2.5 hours B will eventually overtake A, because the speed of B is greater than the speed of A.)
Hence, speed of B is 7 km/hr