Logic Exercise

I ran across this logic exercise in Popular Science, written by Claire Maldarelli, and thought it interesting.  I tried for several days to figure it out, but ultimately, had to look at her answer to get the solution.  I know you will do much better:

A Kindergartner, a fifth grader, a high school track star, and an Olympic sprinter are all waiting in line at a Track & Field meet’s food stand.  Suddenly, the storm of the century rolls in and the only way back to the safety of the stadium is across a wobbly bridge in critical need of repair. 

The rickety old thing can handle only two people crossing at one time. 

The sky is completely black, but luckily, the Kindergartner has a flashlight key chain attached to his backpack.

The wind that will destroy the bridge arrives in 17 minutes.

The Olympic sprinter can cross the bridge in 1 minute.

The high school track star in 2 minutes.

The fifth grader in 5 minutes.

The kindergartner in 10 minutes.

One of the travelers must have a flashlight in their hand.

The minutes are counted as they traverse back and forth across the bridge (the return trip time is counted also).

Scroll down for the answer

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The Olympic sprinter and the high school track star cross together first (2 minutes).

The Olympic sprinter dashes back with the light in hand (1 minute, Total =3)

Then the fifth grader and the kindergartner run across with the light (10 minutes, Total=13

The high school track star, waiting on the other side, rushes back with the flashlight to get the Olympian (2 minutes, Total=15).

Together, they run across just before the bridge collapses (2 minutes)

Total Time: 17 minutes