List of top Quantitative Aptitude Questions on Sequence and series

The next number in the sequence 3, 6, 11, 18, 27, _ _ _ _ is
The average of a non-decreasing sequence of N numbers \(a_1,a_2,…,a_N\) is 300.If \(a_1\) is replaced by \(6a_1\), the new average becomes 400.Then,the number of possible values of \(a_1\) is
The average of all 3-digit terms in the arithmetic progression 38,55,72,...,is