A car moves with velocity 40km/hr for the first half distance and moves with speed 60km/hr for the second half distance. The average speed of the car is...???
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let a = average speed for the trip
let d = half the distance
write a time equation, time = dist/speed
d/40+d/60 = 2d/a
we don't need d, divide by 'd' and you have
1/40+1/60 = 2/a
multiply by 120a to clear the denominators, results:
3a + 2a = 120(2)
5a = 240
a = 240/5
a = 48km/hr
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