A car travels 30 km a
uniform speed of 20km/h
find its average speed
Answers
Step-by-step explanation:
Speed=Distance / time
.°. Time =dist / speed
Let's see the first case,
s = distance = 30 km
v = speed = 40 km/hr
t = time = 30 / 40
=3/4 hrs
Let's see the second case,
s = 30 km
v = 20 km/hr
t = 30 / 20
t = 3/2 hrs
Avg. Speed =Total distance/ Total time
=(30 + 30) / (3/4) + (3/2)
=60 / ( 3 + 6 ) /4
=60 / 9 × 4
=20 / 3 × 4
=80 / 3
=26.67 ( Approx. )
Hence,
Average speed of the car is 26.67 km/hrs ( Approx. )
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Given that,
1st 30 km uniform speed is (u1) = 40 km/h
2nd 30 km uniform speed is ( u2 ) = 20 km/h
Total distance ( d ) = 30 + 30 = 60 km
Time taken in 1st time = d / t = 30/40 also, 3h / 4 = 180/4 = 45 min
Time taken in 2nd time = d/t = 30/20 also, 3h/2 = 180/2 = 90 min
Total time = 45 + 90 = 135 min = 135/60 h
Average speed = 60/135/60 = 60 * 60 /135 = 26.66 km/h