Question

Suppose a car can travel at an average speed of 60 km/h from City A to B. If the car travels at an average speed of 72 km/h, it would reach City B 15 minutes earlier. Calculate the distance between A and B.

A. 60 km
B. 90 km
C. 120 km
D. 150 km

Answer 1

By using the relationship between speed, distance, and time, and setting up equations based on the given speeds and time difference, we find that the distance between City A and City B is 90 km. So the correct answer is Option B.

Step-by-step explanation:

To calculate the distance between City A and City B, we need to use the information that the car travels 15 minutes faster when it increases its speed from 60 km/h to 72 km/h. Let's denote the distance between the cities as d and the time it takes at 60 km/h as t hours.

Using the formula average speed = distance / time, we have the following two equations:

• 60 km/h = d / t
• 72 km/h = d / (t - 0.25), since 15 minutes is 0.25 hours
  

Solving these two equations simultaneously gives us:

• 60t = d
• 72(t - 0.25) = d

Solving for d, we get:

• 60t = 72t - 18
• 12t = 18
• t = 1.5 hours
• d = 60 * 1.5
• d = 90 km

Therefore, the distance between City A and City B is 90 km.