Multiple choice

A car travelling at a constant speed takes $50$ seconds longer to travel a distance of $5$ miles than it would take to travel at $72$ miles per hour. What is the speed of the car?

  1. $40$
  2. $50$
  3. $60$
  4. $70$
  5. $80$
Reveal answer Fill a bubble to check yourself
C Correct answer
Explanation

Let v be the speed in mph. Time to travel 5 miles at v is 5/v hours. Time at 72 mph is 5/72 hours. 5/v - 5/72 = 50/3600 hours = 1/72 hours. 5/v = 6/72 = 1/12. v = 60 mph.

AI explanation

Converting 50 seconds to hours gives 50 divided by 3600, which equals 1/72 hours. The time to travel 5 miles at 72 miles per hour is 5 divided by 72, which equals 5/72 hours, so the slower car takes 5/72 plus 1/72, equaling 6/72 or 1/12 hours. Using the formula Speed equals Distance divided by Time, the car's speed is 5 divided by 1/12, giving 60 miles per hour.

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