Question 942085
s = d/t
d = st
t = d/s
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time from home to store (a):
a = 12 minutes * (1/60 hour/minutes)
a = 12/60 hours
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distance from home to store:
d = st
d = 20t
t = a
d = 20*12/60
d = 4 miles
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time from store to home (b):
t = d/s
b = 4/60 hours
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total time:
a + b = 12/60 + 4/60
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average speed for the round trip:
s = (2*4)/(a + b)
s = 8/(12/60 + 4/60)
s = 30 mph
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