Two soap bubbles, each of radius r, coaleses in vacuum under isotermal conditions to from a bigger bubble of radius R. Then R is equal to

Two soap bubbles of radii 2 cm and 5 cm coalesce under isothermal condition in vaccum, to form a bigger bubble. Find the radius of new bubble.

Two spherical soap bubbles of radii r_(1) and r_(2) in vacuum combine under isothermal conditions. The resulting bubbles has a radius equal to

Two spherical soap bubbles of radii r_1 and r_2 in vacuume coalesce under isothermal condition. The resulting bubble has radius R such that

Two spherical soap bubbles of radii r_1 and r_2 in vacuume coalesce under isothermal condition. The resulting bubble has radius R such that