Question

Iron Man Training While training for an iron man competition, Tony bikes for 60 miles and runs for 15 miles. If his bikes speed is 8 times his running speed and takes 5 hours to complete the training. How long did he speed on his bike

I know the answer is "5/3 hr or 1 hr, 40 min" from the book BUT I don't know how to show the work because it's hard problem so please help me. Thank you

Answer 1

Tony biked 1 hour 40 minutes and run 3 hours 20 minutes.

Explanation:

How long did Tony speed on his bike?

Let s to be Tony's running speed, then 8s is Tony's biking speed

Let's recall that Time = Distance/Speed

Bike time + Running time = 5 hrs

Replacing with the real values, we have:

60/8s + 15/s = 5

8s as Lowest Common Denominator

60 + 8 * 15 = 5 * 8s

60 + 120 = 40s

-40s = -180

s = -180-40

s = 4.5 ⇒ 8s = 36

Tony run at 4.5 mph and biked at 36 mph

Now, we can calculate the time, this way:

Bike time = Bike distance/Bike speed

Replacing with the real values, we have:

Bike time = 60/36

Bike time = 5/3 (Dividing by 12)

5/3 hours * 60 = 100 minutes or 1 hour 40 minutes

Running time = 5 hours - 1 hour 40 minutes = 3 hours 20 minutes

Tony biked 1 hour 40 minutes and run 3 hours 20 minutes.