First puzzle;
2
Second Puzzle:
Take one nut off the remaining three wheels and use them on the one that had none.
Third Puzzle:
Hawaii? the water at 20 degrees F would be frozen so it probably wouldn't fall as fast as in the 40 degree water.
Fourth Puzzle:
I'm not sure about that one: How about this? you put all the pennies standing on thier side so that there are no pennies facing heads up.
TimB