The circumferences of two circles are touching externally. The distance between their centres is 12 cm. The radius of one circle is 7 cm. Find the diameter(in cm) of the other circle.
The ratio of the curved surface area and total surface area of a right circular cylinder is 2 : 5. If the total surface area is 3080 cm2, then what is the volume (in cm3) of the cylinder?
Product of digits of a 2-digit number is 15. If we add 18 to the number, the new number obtained is a number formed by interchange of the digits. Find the number.