Question

Difficulty: MediumCalculating Distance

A dispatch rider is transporting urgent documents between two military installations. The rider travels on a paved highway at a constant speed of 65 mph65\text{ mph} for 1 hour and 12 minutes1\text{ hour and } 12\text{ minutes}. Upon reaching a rural sector, the rider continues on an unpaved route at a steady speed of 42 mph42\text{ mph} for 35 minutes35\text{ minutes}. What is the total distance, in miles, the dispatch rider traveled?

Answer: 102.5 miles

Answer

102.5
To find the total distance, calculate the distance for each leg of the trip separately by ensuring time is expressed in hours. For the first leg, 1 hour and 12 minutes1\text{ hour and } 12\text{ minutes} is 1.2 hours1.2\text{ hours}. Multiplying the 65 mph65\text{ mph} rate by 1.2 hours1.2\text{ hours} gives 78 miles78\text{ miles}. For the second leg, 35 minutes35\text{ minutes} is 3560\frac{35}{60} or 712 of an hour\frac{7}{12}\text{ of an hour}. Multiplying the 42 mph42\text{ mph} rate by 712 hours\frac{7}{12}\text{ hours} gives 24.5 miles24.5\text{ miles}. Adding these two distances together (78+24.578 + 24.5) gives a total of 102.5 miles102.5\text{ miles}.

Step-by-Step Solution

1
Convert the highway travel time into hours.
1 hour and 12 minutes=1+1260 hours=1.2 hours1\text{ hour and } 12\text{ minutes} = 1 + \frac{12}{60}\text{ hours} = 1.2\text{ hours}.
The speed is given in miles per hour, so time must be converted to hours to match units.
2
Calculate the distance traveled on the highway.
65 mph×1.2 hours=78 miles65\text{ mph} \times 1.2\text{ hours} = 78\text{ miles}.
Applying the formula: Distance = Rate ×\times Time.
3
Convert the unpaved route travel time into hours.
35 minutes=3560 hours=712 hours35\text{ minutes} = \frac{35}{60}\text{ hours} = \frac{7}{12}\text{ hours}.
Time must be in hours for consistency with the speed unit.
4
Calculate the distance traveled on the unpaved route.
42 mph×712 hours=24.5 miles42\text{ mph} \times \frac{7}{12}\text{ hours} = 24.5\text{ miles}.
Applying the formula: Distance = Rate ×\times Time.
5
Calculate the total distance.
78 miles+24.5 miles=102.5 miles78\text{ miles} + 24.5\text{ miles} = 102.5\text{ miles}.
The total journey distance is the sum of the individual distances from each leg.

Key Concept

Calculating total distance for a multi-leg journey by accurately converting fractional times to hours and applying the distance formula.
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