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 remaini

Question 1019106: 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?

Found 3 solutions by jorel555, MathTherapy, ikleyn:
Answer by jorel555(1290)   (Show Source): You can put this solution on YOUR website!
The first mile is at 12 mph, which would take 5 minutes to finish. The second mile takes 10 minutes, which is 60/10, or 6 mph. The average for the two miles is 12+6/2, or 9 mph!!!!!!!!!!!!
Answer by MathTherapy(10552)   (Show Source): You can put this solution on YOUR website!

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?

Speed for 2nd leg:
Average speed: , or
Answer by ikleyn(52787)   (Show Source): You can put this solution on YOUR website!
.
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?
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"the first half of the distance he biked at a speed of 12 mph". So, Ling biked 1 miles at the speed of 12 mph = = 0.2 miles per minute. Thus Ling spent = 5 minute to cover the first half of the distance. For the second half, which is also 1 mile, Ling spent the remaining 15-5 = 10 minutes, i.e. twice the time he spent for the first mile. It means that his speed was half of the speed on the first mile, = 6 mph. It is the answer to the first question. Regarding the average speed, it is the FULL distance divided by the FULL time, i.e. = = 2*4 = 8 mph. (Here is 15 minutes = 1/4 of an hour.) Answer. The Ling's speed on the second half of the distance was 6 mph. The average speed was 8 mph. The solution by jorel555 is wrong in this part. The error he made is TYPICAL and represents the good/classic example on how this problem SHOULD NOT be solved.

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