A group of 630 children seated in rows for a group photo session. Each row contains three less children than the row in front of it. Which one of the following number of rows is not possible?

Along a 300 m long road, 16 electric poles are fixed at equal distances, one pole being at each end of the road. What is the distance between two consecutive poles?

What is the 30th term of the following arithmetic series? 4, 8, 12, 16, ...

If the 3rd term of a geometric progression is 2, then the product of first 5 terms of the series is

If the sum the first 11 terms of an arithmetic progression equals that of the first 19 terms, then the sum of first 30 terms will be

If the 3rd term of an A.P. is 1/5 and the 5th term is 1/3, then the 15th term of the series is