This is a classic unilateral contract offer, and I'm guessing it will be on all the first year contract exams next year. In a unilateral contract, you offer something to someone (someone specific or anyone in general) and they can only accept the contract by performing the terms in their entirety. It is not enough to say "I accept your offer" and it is not enough to try and fail; you must complete the terms offered. Contrast this with a bilateral contract where you form a binding contract by saying "I accept" or words to that effect.

The traditional example is a reward. Rewards are almost never paid, at least not the large ones for catching a vial criminal because the person trying to collect usually cannot show that they did the required conduct because of the offer. Heck, they usually catch the guy breaking into their home and either did not know of the reward, or suffer from catching him because they were defending themselves, not because of the reward. In this case, however, the student appears to have heard the offer and done the experiment on that basis. Note that if he had taken 29 minutes to complete the trip, he would be entitled to NOTHING, not even expenses.

Yes, IAAL, but I am not your L.

Math Fail!

Obviously you don't play craps. When you throw 2D6, there is a 6 in 36 chance of comming up seven, not the 1 in 12 chance you seem to assume. Try this thought experiement: What are all the combinations for each potential number between 2 and 12 when you throw 2D6? I'll give you a hint, there is only one way each to get 2 or 12. Now, if you take mod 8 and add 1 of the result, you have heavily weighted the middle numbers