B) David and Andrew are traveling to a Mathematics conference. David travels 110 miles in the same time that Andrew travels 140 miles. Andrew travels 15 miles per hour faster than David. Find the average rate of each person.
1 answer:
Answer:
David's average speed is 55 mph and Andrew's average speed is 70 mph
Step-by-step explanation:
Let David's speed be s.
Average speed is given as:
speed = distance / time
They both spent the same time, t.
David's speed is:
s = 110 / t
=> t = 110 / s
Andrew travels 15 mph faster than David.
Andrew's speed is:
(15 + s) = 140 / t
=> t = 140 / (15 + s)
Therefore, since they spent the same time:
110 / s = 140 / (15 + s)
Cross multiply:
110(15 + s) = 140s
1650 + 110s = 140s
1650 = 140s - 110s
30s = 1650
s = 1650 / 30
s = 55 mph
Andrew's speed is:
15 + 55 = 70 mph
Therefore, David's average speed is 55 mph and Andrew's average speed is 70 mph .
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