A bank offers 20% compound interest per half year. A customer deposits Rs 6000 each on 1st January and 1st July of a year. At the end of the year, the amount he would have gained by way of interest is
The distance between the centres of two circles is 61 cm and their radii are 35 cm and 24 cm. What is the length (in cm) of the direct common tangent to the circles?