Adobe - Puzzles Questions asked for fresher

Adobe - Puzzles Questions asked for fresher
1)There is a clock at the bottom of the hill and a clock at the top of the hill. The clock at the bottom of the hill works fine but the clock at the top doesn't. How will you synchronize the two clocks. Obviously, you can't carry either of the clocks up or down the hill! And you have a horse to help you transport yourself. And, the time required for going up the hill is not equal to the time required to go down the hill.

Answer : You have to go up the hill and come back, with horse, without horse, getting four equations to solve four unknowns - time to go uphill - with horse, without horse, time to go downhill - with horse, without horse. Then you can go up the hill and set the clock to '(time when you left) + (time to go uphill with horse)'

2).There was one more puzzle.. I don't remember it. but I do remember that we started discussing ways of generating large prime numbers. I told him the funda of Mersenee primes (luckily remembered it) and he was decently impressed.