The radius of the large sphere is twice
the radius of the small sphere.

Answer:
40 cm²
Step-by-step explanation:
Given the ratio of radii = a : b , then
ratio of areas = a² : b²
Here ratio of radii = 1 : 2
ratio of areas = 1² : 2² = 1 : 4
Thus
surface area of large sphere = 4 × 10 = 40 cm²