Question

A train travelled 65% of the way from town Bombay to town Bangalore by travelling for A hours at an average speed of B km/hr. The train travels at an average speed of S km/hr for the remaining part of the journey. Which of the following expressions represents the average speed of the entire journey?​

Answer 1

Answer:

35%the speed is 60kmph

Explanation:

the speed of train is ,60 kmph per hour

Answer 2

Answer:

average speed of the entire journey  is given by the expression$v=\frac{1}{\frac{65}{100B}+\frac{35}{100S} }$

Explanation:

Let us say the total distance  from Bombay to Bangalore is x km.

Train travels 65 % of the way in A hour at an average speed of B km/hr

so distance travelled=$\frac{65}{100}x$

time taken for this is A which is given as

$time=\frac{distance}{speed}$⇒$A=t_1=\frac{65x}{100*B}$

train travels next 35% of the journey with a speed of S km/hr,

hence the time take for that , let us say $t_2=\frac{35x}{100*S}$

total time taken =$t=t_1+t_2=\frac{65}{100B}+\frac{35}{100S}$

⇒average speed of the entire journey $v=\frac{x}{\frac{65x}{100B}+\frac{35x}{100S} }=\frac{1}{\frac{65}{100B}+\frac{35}{100S} }$