1. 13 balls are given of which only 1 is different. We do not know whether the given is heavier or lighter. How will you determine in just three measurments, the odd ball?

2.If the day after tomorrow was yesterday, then Sunday would be what today was. If the day before yesterday was the day after tomorrow, then what is today?

3. Find the probability that in a gathering of 50 people,two persons birthday fall in the same day.

4. How many balls can be placed around one ball of the same size so that the later touches each of the former one.