Problema Solution

On the first day of a two day vintage car rally, Mr. and Mrs. Harrington drove 90 miles in their

1940 Chevrolet Cabriolet. On the second day they were able to average 20 mph faster

by driving their 1968 Ford Mustang, and they traveled a total of 100 miles. If the total driving

time for the two days was 5 hours, what was their average speed in each of the vehicles?

Answer provided by our tutors

let


d1 = 90 mi

v = the average speed of the first day

d2 = 100 mi

v + 20 = the average speed on the second day was 20 mph faster then on the first day

t = 5 hr the total driving time for the two days


since avg.speed = total distance/time => time = total distance/avg.speed


v/d1 + (v + 20)/d2 = 5


v/90 + (v + 20)/100 = 5


by solving the equation we find


v = 227.37 mph


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v + 20 = 247.37 mph


the average speed on the first day in the 1940 Chevrolet Cabriolet was 227.37 miles per hour.

the average speed on the second day in the 1968 Ford Mustang was 247.37 miles per hour.