1.

If a car gocs from a place X to aplace Y with a speed of 60 km/hand returns from Y to X with a speedof 40 km/h, what is its average speedfor the whole journey ?

Answer»

Let the Distance travelled by man = x km

Speed (S1) = 40 km/h

Speed (S2)= 60 km/h

Time taken by man to travel from city B to C(T1)= Distance/ speed(s1)

T1= x/40= x/40 h

Time taken by man to return from city C to B(T2)= Distance/ speed(s2)

T2= x/60

Total time taken (T) = T1+T2

T= x/40+x/60=( 3x+2x)/120= 5x/120

T= x/24 h

Total distance (D)= x+x= 2x

Average speed= Total Distance (D)/Total time (T)

Average speed = D/T= 2x / (x/24)

= 2x×( 24/x)= 48 km/h

Hence, His average speed for the round trip= 48 km/hr

48 km/hr is the answer



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