a car moving on a straight road covers the 1/4th of the distance 36km/h and the rest with 54 km/h, the average speed of the car is?
a) 11/3 m/s
b) 40/3 m/s
c) 27 m/s
d) 18m/s
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Answer:
b)
Explanation:
let total distance be x
while travelling x/4 distance,
speed= 36 km/h or 36× 5/18 m/s or 10 m/s
time= distance / speed
time= x/4 ÷10
time=x/40 s
while travelling 3/4 distance,
speed= 54 km/h or 15 m/s
time= distance/ speed
time= 3x/4÷15
time= 3x/60
time= x/20
avg speed= total distance / total time
= x/(x/40 +x/20)
=x/3x/40
=40x/3x
=40/3 m/s
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