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25. During the first 20 miles of a 50 mile bicycle race,Roger's average speed was 16mi/h. what must his average speed be during the remainder of the race if he is to finish the race in less than 2.5 hours? Greater than:

A) 24mi/h

B)8mi/h

C)12mi/h

D) 4mi/h

distance = time x speed. So, during the first 20 miles, he averaged 16mph, so fill those values into your equation and solve for time. 20=16t or time = 20/16 = 5/4 = 1 1/4 = 1 hr, 15 mins. So, now the rider has to do 30 miles in less than 1hr, 15mins (5/4). So again, fill those values into your equation 30=5/4s. Multiplying both sides of the equation by 4/5 gives you

30(4/5)=5/4(4/5)s = s = 120/5 = 24. So, Roger needs to average greater than 24 to finish in 2.5 hrs.

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