Multiple choice

A toy car was moving; and after it had travelled 9 miles, a dog started chasing it with double the speed of the car from the same point the car had left. Find the distance from the starting point in which the dog would catch the car.

  1. 10 miles

  2. 18 miles

  3. 20 miles

  4. 25 miles

  5. 35 miles
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation

Let the car speed be v. The dog's speed is 2v. The car has a 9-mile head start. Time for dog to catch car = (Head start distance) / (Relative speed) = 9 / (2v - v) = 9/v. Distance covered by dog = Speed * Time = 2v * (9/v) = 18 miles.

AI explanation

Let the speed of the car be v and the speed of the dog be 2v; when the dog starts, the car has a 9 mile lead. Using the relative speed method, the dog catches the car at a rate of 2v minus v, which is v miles per hour. The time taken to close the 9 mile gap is 9/v hours, and the distance the dog travels in that time is 2v multiplied by 9/v, equaling 18 miles from the starting point.

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