SOLUTION: two towns are 80 km apart . kasia wants to drive from one town to the other in exactly one hour. for the first 30 minutes she drives at a rate of 60 km/h. the constant rate , in km

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Question 237582: two towns are 80 km apart . kasia wants to drive from one town to the other in exactly one hour. for the first 30 minutes she drives at a rate of 60 km/h. the constant rate , in km/h, at which she must drive for the next 30 minutes to accomplish her goal is
(a) 20 (b) 40 (c) 50 (d) 80 (e) 100
Answer by Theo(13342) About Me  (Show Source):
You can put this solution on YOUR website!
distance = rate * time

t = 1
d = 80 km

first part of the trip, rate * time was .5 * 60
second part of the trip, rate * time will be .5 * x

add the parts together to get the total trip.

.5 * 60 + .5 * x = 80

30 + .5x = 80

subtract 30 from both sides to get:

.5x = 50

divide both sides by .5 to get:

x = 100

confirm by plugging into the original equation to get:

.5 * 60 + .5 * 100 = 80

simlify to get:

30 + 50 = 80 confirming the answer for x is good.

looks like she will have to drive 100 km/h in order to achieve her goal of driving 80 km in exactly 1 hour.