The surface area of a cube whose edge is $a$ is: (in $a^{2}$)

The surface area of a sphere is $7850 \, cm^2$. Find its radius in $cm$. (Use $\pi = 3.14$)

$A$ room without a ceiling is $12 \, m$ long,$4 \, m$ wide,and $3 \, m$ high. Find the length of the longest rod that can be placed in that room. (in $m$)

The water for a factory is stored in a hemispherical tank whose internal diameter is $14\, m$. The tank contains $50\, kilolitres$ of water. Water is pumped into the tank to fill it to its capacity. Calculate the volume of water pumped into the tank (in $m^3$).

The number of planks of dimensions $(4 \,m \times 50 \,cm \times 20 \,cm)$ that can be stored in a pit which is $16 \,m$ long,$12 \,m$ wide,and $4 \,m$ deep is:

Two solid spheres made of the same metal have weights $5920 \, g$ and $740 \, g$ respectively. Determine the radius of the larger sphere,if the diameter of the smaller one is $5 \, cm$. (in $cm$)