The angle of elevation of the top of a tower from the point P and Q at a distance of 'a' and 'b' respectively from the base of the tower and in the same straight line with it are complementary. The height of the tower is:
At a certain rate per annum, the simple interest on a sum of money for one year is Rs. 260 and the compound interest in the same sum for two years is Rs 540.80/-. The rate of interest per annum is