a car covers the first half of the distance between two places at a speed of 60 km/hr. At what speed must it covered the second half so that the average speed for the entire journey is 96 km/hr
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let a = average speed for the trip
let d = half the distance
:
write a time equation, time = dist/speed
d%2F40 + d%2F60 = %282d%29%2Fa
we don't need d, divide thru by d and you have
1%2F40 + 1%2F60 = 2%2Fa
multiply by 120a to clear the denominators, results:
3a + 2a = 120(2)
5a = 240
a = 240/5
a = 48 km/hr
let d = half the distance
:
write a time equation, time = dist/speed
d%2F40 + d%2F60 = %282d%29%2Fa
we don't need d, divide thru by d and you have
1%2F40 + 1%2F60 = 2%2Fa
multiply by 120a to clear the denominators, results:
3a + 2a = 120(2)
5a = 240
a = 240/5
a = 48 km/hr
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