Question Discussion & Solution

The pattern followed here is:

25 → First digit of 23 and second digit of 65.

68 → First digit of 61 and second digit of 38.

? → First digit of 72 and second digit of 48 → 78.

Hence, the answer is 78.

The correct answer is Mr Sachin Pilot.

• As of June 2020, Mr. Sachin Pilot is the Minister of Science and Technology, Panchayati Raj of Rajasthan.

Key Points

• Mr. Sachin Pilot s the Minister of Science and Technology, Panchayati Raj of Rajasthan.
• He is also the current Deputy Chief Minister of Rajasthan.
• His constituency is Ajmer, Rajasthan.
• He is associated with Indian National Congress.

Additional Information

• Mr. Ashok Gehlot is the current Chief Minister of Rajasthan in the Government of Rajasthan.
• Mr. Bulaki Das Kalla is the Minister of Energy, Public Health & Engineering, Ground Water, Art, Literature, Culture & Archeology in the Government of Rajasthan.
• Master Bhanwarlal Meghwal is the Minister of Social Justice and Empowerment in the Government of Rajasthan.

The correct answer is Tropical Deciduous Forests.

Key Points

• Tropical Deciduous Forests
  • These are the most widespread forests in India.
  • They are also called the monsoon forests because the trees in these forests shed their leaves during the dry season and re-grow during the monsoon. Hence, Statement 1 is correct.
  • They spread over regions that receive rainfall between 70-200 cm. 
  • The average temperature of Tropical Deciduous forests is 30oC. Hence, Statement 2 is correct.
  • The humidity in these forests lies in the range of 80-90 per cent.
  • The prime feature of these forests as trees shed their leaves in the dry season and grow back leaf in rainy seasons.
  • Major states where tropical deciduous forests are found:
    • Madhya Pradesh
    • Uttar Pradesh
    • Chhattisgarh
    • Jharkhand
    • Odisha
    • Maharashtra 
    • Some parts of Tamil Nadu and Andhra Pradesh
  • On the basis of the availability of water, these forests are further divided into
    • Moist Deciduous
    • Dry Deciduous
• Moist Deciduous forests
  • They spread over regions that receive rainfall between 100-200 cm.
  • These forests are found in the northeastern states along the foothills of the Himalayas, eastern slopes of the Western Ghats, and Odisha.
  • Teak, Sal, Shisham, Hurra, Mahua, Amla, Semul, Kusum, and Sandalwood, etc. are the main species of these forests. Hence, Statement 3 is correct.​
• Dry Deciduous forests
  • They spread over regions that receive rainfall between 70-100 cm.
  • These forests are found in the rainy areas of Peninsular India, Plains of Uttar Pradesh, and Bihar.
  • In the higher rainfall regions of the Peninsular plateau and the northern Indian plain, these forests have a parkland landscape with open stretches in which teak and other trees interspersed with patches of grass are common.
  • As the dry season begins, the trees shed their leaves completely and the forest appears like a vast grassland with naked trees all around.
  • Tendu, Palas, Amaltas, Bel, Khair, Axlewood, etc. are the common trees of these forests.

Additional Information

• Tropical Thorn Forests
  • Tropical Thorn Forests are found in areas having less than 50cm of Rainfall.
  • A variety of Grasses and Shrubs are found in these thorn forests.
  • They are present in dry and semi-dry areas of south-west Punjab, Haryana, Gujarat,
  • Rajasthan, Madhya Pradesh, and Uttar Pradesh.
  • In Tropical Thorn Forest, Trees remain leafless for the most part of the year
  • Tussocky Grass grows up to 2m in these areas. 
• ​Montane Forests​
  • Evergreen type of vegetation is prevalent in montane forests.
  • Generally, they are conical in shape so that it is easy for the snow to slide down.
  • Montane Forest is an ecosystem found in mountains.
    • These forests can be found in the higher hilly areas of Kerala and Tamil Nadu, also in the region of Eastern Himalayas to the east of 88°E longitude including the hills of Assam, West Bengal, Sikkim, Arunachal Pradesh, and Nagaland.
  • Some significant trees of the montane temperate forest are rhododendrons, ferns, oak, maple, juniper, deodar, chilgoza, etc.
• Tropical Evergreen Forests
  • ​Tropical evergreen forests are dense, multi-layered, and harbor many types of plants and animals.
  • These forests are found in the areas receiving heavy rainfall (more than 200 cm annual rainfall).
  • Therefore, these forests always appear green and are known as evergreen forests.
  • The greatest single area of tropical evergreen forest is the Amazon Basin, in the northern half of South America.
  • In India, evergreen forests are found in the western slopes of the Western Ghats in States such as Kerala and Karnataka. They are also found in the hills of Jaintia and Khasi.
  • Evergreen forests are found in the Assam Valley, the foothills of the eastern Himalayas, and the lower parts of the Naga Hills, Meghalaya, Mizoram, and Manipur.
  • Ebony, mahogany, rosewood, rubber, and cinchona are some of the commercially important trees that grow in the tropical evergreen forests.

CONCEPT:

• Ultrasonic waves are the sound waves with frequencies higher than the upper audible limit of human hearing.
  • They have a short wavelength.
• Echo: If we shout or clap near a suitable reflecting object such as a tall building or a mountain, we will hear the same sound again a little later. This sound which we hear is called an echo.
  • Echoes are heard due to the phenomenon of Reflection of sound waves.
• SONAR: It a technique that uses sound propagation (usually underwater, as in submarine navigation) to navigate, communicate with or detect objects on or under the surface of the water
  • SONAR stands for ‘Sound Navigation and Ranging.’
  • SONAR is based on the principle of echo.
  • Sonar is often used as a measurement of acoustic location and echo characteristics of the target object in the water.
  • It sends ultrasonic waves towards the bottom area of the sea and after reflection, the sound comes to the ship. We measure the time taken by the sound wave and then we get the depth. 

EXPLANATION:​

• From the above discussion, we can say that the SONAR uses the principle of reflection of sound waves(Echo) to detect and locate objects. So option 2 is correct.
• Reverberation: The persistence of sound in a closed enclosure, due to continuous reflections at the walls or the floor or the ceiling of the enclosure, even after the source has stopped producing sound is known as 'reverberation'.

The correct answer is Lead and Tin.

Key Points

• Soldering is the process of joining two metal objects together by a third soft metal alloy which is called solder.
• Solder is a metal alloy that melts at a lower temperature than the metals being soldered.
• A commonly used alloy is solder, which is an alloy of tin (Sn) and lead (Pb).
• The alloy of tin-lead solder is a mixture of 63% tin and 37% lead. 63/37 solder melts at 183°C.
• So, Alloy of tin (Sn) and lead (Pb) is used for welding electrical wire together.

Additional Information

• Element Tin (Sn) belongs to Group 14 of the periodic table.
  • Atomic Number - 50
  • Atomic Mass  - 118.710 amu.
• Element Lead (Pb) belongs to Group 14.
  • Atomic Number - 82
  • Atomic Mass - 207.2 amu.