A number 15 is divided into three parts which are in AP and sum of their squares

A number 15 is divided into three parts which are in AP and sum of their squares is 83. The smallest part is

2) If the roots of the equation (b - c)x2 + (c - a)x + (a-b) = 0 are equal, then

3) The sum of the first ten terms of an AP is four times the sum of the first five terms, then the ratio of the first term to the common difference is

4) If the third term of an AP is 12 and the seventh term is 24, then the 10th term is

5) 25 trees are planted in a straight line 5 metres apart from each other. To water them the gardener must bring water for each tree separately from a well 10 metres from the first tree in line with the trees. How far will he move in order to water all the trees beginning with the first if he starts from the well ?