Math Problem Statement

A person travels by car from one city to another with different constant speeds between pairs of cities. She drives for 20 min at 75 km/hr, 17 min at 100 km/hr, and 47 min at 44 km/hr. She spends 24 min eating lunch and buying gas. 

What is the distance between the two cities?

(Remember to convert between minutes and hours.)

Solution

To find the total distance between the two cities, we'll need to calculate the distance traveled at each speed and then sum these distances.

Step 1: Convert minutes to hours

  • 20 minutes at 75 km/hr:
    Time in hours=2060=13 hours\text{Time in hours} = \frac{20}{60} = \frac{1}{3} \text{ hours}

  • 17 minutes at 100 km/hr:
    Time in hours=1760 hours\text{Time in hours} = \frac{17}{60} \text{ hours}

  • 47 minutes at 44 km/hr:
    Time in hours=4760 hours\text{Time in hours} = \frac{47}{60} \text{ hours}

Step 2: Calculate the distance for each segment

  • Distance for the first segment: Distance=75km/hr×13hr=25km\text{Distance} = 75 \, \text{km/hr} \times \frac{1}{3} \, \text{hr} = 25 \, \text{km}

  • Distance for the second segment: Distance=100km/hr×1760hr28.33km\text{Distance} = 100 \, \text{km/hr} \times \frac{17}{60} \, \text{hr} \approx 28.33 \, \text{km}

  • Distance for the third segment: Distance=44km/hr×4760hr34.47km\text{Distance} = 44 \, \text{km/hr} \times \frac{47}{60} \, \text{hr} \approx 34.47 \, \text{km}

Step 3: Sum the distances

Total Distance=25km+28.33km+34.47km87.8km\text{Total Distance} = 25 \, \text{km} + 28.33 \, \text{km} + 34.47 \, \text{km} \approx 87.8 \, \text{km}

The total distance between the two cities is approximately 87.8 km.

Do you have any questions, or would you like further details?


  1. How do you convert minutes into hours?
  2. How do you calculate distance if speed and time are given?
  3. What is the significance of adding up distances in different segments of a journey?
  4. How would the problem change if the time spent during lunch was included in the travel time?
  5. What would be the effect on the total distance if one segment was traveled at a different speed?

Tip: Always ensure time is converted to the same unit when calculating distance, especially when dealing with speeds given in km/hr.

Ask a new question for Free

By Image

Drop file here or Click Here to upload

Math Problem Analysis

Mathematical Concepts

Distance Calculation
Speed-Time-Distance Relationship
Unit Conversion

Formulas

Distance = Speed × Time
Time in hours = Time in minutes ÷ 60

Theorems

-

Suitable Grade Level

Grades 6-8