A man has some hens and some cows. If the total number of heads of hens and cows together is 50 and the nunber of feet of hens and cows together is 142, then the number of cows is
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?