Two circles of same radius intersect each other at P and Q. If the length of the common chord is 30 cm and distance between the centres of the two circlesis 40 cm, then what is the radius (in cm) of the circles?
Before Champaran Satyagraha, the farmers of Champaran used to follow the 'Panchkathiya' system, whereby five katthas of land in a bigha had to be planted with ___.