Question Discussion & Solution

The pattern is:

31

31 × 2 + 1 = 63;

63 × 2 - 2 = 124;

124 × 2 + 3 = 251;

251 × 2 - 4 = 498

Hence, the answer is '498'.

The correct answer is Open Cast Mining.

• Open Cast Mining is the process under which minerals are mined near the earth's surface.

Key Points

• Opencast mining is the process that involves the removal of ore from seams relatively near the surface by means of an open-pit.
• These mines occupy a large area of land for excavation of the ore and disposal of the overburden.

Additional Information

• Drilling is a cutting process which uses a drill bit to cut a hole of circular cross-section in solid materials or ground.
• Quarrying is the process of removing rock, sand, gravel or minerals from the ground in order to use them to produce materials for construction or other uses.
• Shaft mining is the process where miners dig straight down until they reach their desired depth. 

Energy is a phenomenon which is transferred from one object to another in the form of heat, as a result, it performs work. When the energy is transferred from one object to another, it changes its form and this phenomenon is called conservation of energy. The following types of energy are discussed below:

• Solar Energy: It is the energy that is derived from the sun. When solar cells are exposed to the sun, it converts solar energy in electrical energy. Important facts related to the solar energy:
  • India ranks 5^th globally in the installed Solar Energy.
  • India has about 34.5 GW installed solar capacity at present.
  • Ndia targes 175 GW of renewable energy by 2022.
• Chemical Energy: It is the energy that is released when a chemical reaction takes place. Its applications are in the creation of energy in our body, photosynthesis, electric cells.
• Nuclear Energy: This energy is either produced by nuclear fusion or nuclear fission. Nuclear fusion is a process when two nuclei are combined to release energy while nuclear fission is a process in which a single nucleus breaks into two parts to release energy.
• Magnetic Energy: Energy caused by the production of the magnetic field is called magnetic energy. This energy is used in making electrical bells, electric motors and generators.

Hence, we conclude that solar energy causes solar energy to transform electrical energy.

Explanation:

• The metallic property of the elements of the periodic table decreases when we move across the group whereas it increases when we go down the group, as we go down the number of electrons increases and thereby their distance from the nucleus increases. 
• This increase causes them to shed more electrons and thereby have a greater electropositive or metallic character. 

Among the given compounds Na shows maximum Metallic character. 

Here the pattern is,