A and B together can finish a work in 30 days. They worked for it for 20 days and then B left the work. The remaining work was done by A alone in 20 days more. In how many days can A alone finish the work?
Two circles touch each other internally. The radius of the larger circle is 6 cm and the distance between the centre is 2 cm, then the radius (in cms) of the other circle is