There are four people that want to cross a bridge. Sam can cross in 1 minute, Joe can cross in 2, Jack can cross in 5, and Steve can cross in 10. They have one flashlight, and two can cross at a time, but they must go at the same pace. So if Steve and Sam cross together, they must go at 10 minutes. The partners must use a flashlight, and one must bring it right back. They must cross in 16 minutes or less. How?

To solve this puzzle, we need to come up with a plan that ensures all four people cross the bridge in 16 minutes or less. Here is the step-by-step explanation:

1. First, Sam and Joe will cross the bridge together with the flashlight, taking 2 minutes. Sam will bring the flashlight back to the starting point, taking an additional 1 minute. So far, 3 minutes have passed.

2. Next, Steve and Jack will cross the bridge together with the flashlight, taking 10 minutes. Steve will bring the flashlight back, taking an additional 1 minute. Now, a total of 14 minutes have passed.

3. Finally, Sam and Joe will cross the bridge together again, taking 2 minutes. This completes the puzzle within the time limit of 16 minutes.

In summary, the plan is as follows:

- Sam and Joe cross the bridge (2 minutes)
- Sam brings the flashlight back (1 minute)
- Steve and Jack cross the bridge (10 minutes)
- Steve brings the flashlight back (1 minute)
- Sam and Joe cross the bridge again (2 minutes)

By following this plan, all four people can cross the bridge in 16 minutes or less.