Jessica was driving her car and maintains an average speed of 35 kilometers per hour. She passed a church at 8 a.m. Andrew was also driving along the same route and passed the same church at 10 a.m. He overtook Jessica's car at noon. In kilometers per hour, at what rate was Andrew driving his car?

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Answers

2014-10-06T20:04:16+08:00
We let the church be the reference point of both cars.
Since Jessica passed the church at 8am and was overtook by Andrew's car at 12noon then the time traveled by Jessica is 4 hours.
Finding the total distance traveled by the car you'll have:
v(velocity) =  \frac{d(distance)}{t(time)}
rearranging the formula
d = vt
d = 35km/hr(4hrs)
d = 140 km
we know that this same distance was traveled by Andrew before overtaking and that he passed the church at 10am and got to overtake at 12nn which makes the travel time 2hours.
Still using the same formula for velocity, knowing that d=140 you'll have:
v =  \frac{d}{t}
v =  \frac{140km}{2hrs}
v = 70 kph
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