Problema Solution
Ling lives 2 miles from school. It took him 15 minutes to bike from school to home. The first half of the distance he biked at a speed of 12 mph. What was his speed for the remaining distance? What was his average speed?
Answer provided by our tutors
Let
v1 = 12 mph
v2 = the speed of the second half
v = the average speed
t = 15 min = 15/60 hr = 1/4 hr = 0.25 hr
d = 2 mi
d/2 = 2/2 = 1 mi (half the distance)
Since speed = distance/time follows time = distance/speed:
(d/2)/v1 + (d/2)/v2 = t
1/12 + 1/v2 = 0.25
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click here to see the equation solved for v2
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v2 = 6 mph
v = d/t
v = 2/0.25
v = 8 mph
The speed for the remaining distance is 6 mph.
The average speed for the whole trip is 8 mph.