Step 1: Understanding Energy Minerals
Energy minerals are those that are used as sources of energy. These include coal, natural gas, and uranium. They are used for power generation, heating, and industrial purposes.
Step 2: Why the other options are energy minerals
- (B) Coal: Coal is an energy mineral used for electricity generation and as a fuel for various industrial processes.
- (C) Natural Gas: Natural gas is a key energy resource used for heating, electricity generation, and as a raw material for various chemicals.
- (D) Uranium: Uranium is used as fuel in nuclear reactors for energy production.
Step 3: Why Iron-ore is not an energy mineral
- (A) Iron-ore: Iron-ore is a metallic mineral used primarily for the production of iron and steel, not for energy production.
Thus, the correct answer is option (A) Iron-ore.
Find the unknown frequency if 24 is the median of the following frequency distribution:
\[\begin{array}{|c|c|c|c|c|c|} \hline \text{Class-interval} & 0-10 & 10-20 & 20-30 & 30-40 & 40-50 \\ \hline \text{Frequency} & 5 & 25 & 25 & \text{$p$} & 7 \\ \hline \end{array}\]
Two concentric circles are of radii $8\ \text{cm}$ and $5\ \text{cm}$. Find the length of the chord of the larger circle which touches (is tangent to) the smaller circle.