RRB Group D flashcards

32 cards. Read the term and the definition here. The deck at the top of this page is optional.

Speed unit conversion

Multiplying a speed in km/h by 5/18 gives the value in m/s, and multiplying a speed in m/s by 18/5 gives km/h. Example: 72 km/h = 20 m/s.

Compound interest formula

The amount is A = P(1 + r/100)^n, where P is principal, r the annual rate and n the number of years. Compound interest equals A minus P.

HCF and LCM relation

For any two positive integers, the product of the numbers equals the product of their HCF and LCM. This lets you find one value when the other three are known.

Sum of first n naturals

The sum 1 + 2 + 3 + ... + n equals n(n+1)/2. For example, the sum of the first 10 natural numbers is 10 × 11 / 2 = 55.

Circle area and circumference

For a circle of radius r, area equals πr² and circumference equals 2πr. Diameter is twice the radius, so area can also be written as πd²/4.

Simple interest formula

Simple interest equals (P × R × T)/100, where P is principal, R the rate per cent per year and T the time in years. The amount is principal plus interest.

Average of observations

Average equals the sum of all observations divided by the number of observations. If every value is increased by k, the average also increases by k.

Divisibility by eleven

A number is divisible by 11 if the difference between the sum of its digits in odd places and the sum in even places is 0 or a multiple of 11.

Odd days in a century

In the calendar system, 100 years contain 5 odd days, 200 years contain 3, 300 years contain 1 and 400 years contain 0 odd days, since 400 years is an exact multiple of 7.

EJOTY letter positions

The letters E, J, O, T and Y occupy positions 5, 10, 15, 20 and 25 in the alphabet. Counting forward or backward from these anchors locates any letter quickly.

Mirror image rule

In a mirror image the left and right sides of the figure are interchanged while the top and bottom remain in place, producing a horizontal reversal about a vertical line.

Water image rule

In a water image the top and bottom of the figure are interchanged while the left and right remain in place, producing a vertical reversal about a horizontal line.

Standard die opposite faces

In a standard die, faces that lie opposite each other always add up to 7. Therefore 1 and 6, 2 and 5, and 3 and 4 can never be seen adjacent.

Direction and displacement

For a path with net movement x in one perpendicular direction and y in the other, the shortest distance from start to finish is √(x² + y²), from the Pythagorean theorem.

Syllogism all-and-some

If all A are B, then A lies inside B, so 'some B are A' is a valid conclusion while 'all B are A' is not. Conclusions must hold in every possible diagram.

Coding by letter shift

When each letter of a word is replaced by the letter a fixed number of places ahead or behind it, the code is broken by finding that constant shift from any one pair of letters.

Newton's second law

The force acting on a body equals its mass multiplied by the acceleration produced, F = ma. The SI unit of force is the newton, equal to kg·m/s².

Ohm's law

At constant temperature, the current through a conductor is directly proportional to the potential difference across it, V = IR, where R is resistance in ohms.

pH scale meaning

The pH scale runs from 0 to 14 and measures hydrogen ion concentration. Values below 7 are acidic, 7 is neutral, and values above 7 are basic or alkaline.

Photosynthesis equation

In the presence of sunlight and chlorophyll, plants combine six molecules of carbon dioxide with six of water to form one glucose molecule and release six molecules of oxygen.

Bones in adult body

A fully grown human has 206 bones, while a newborn has about 300, because many separate bones fuse during growth. The longest bone is the femur.

SI unit of power

Power is the rate of doing work, measured in watts. One watt equals one joule per second, and one horsepower is approximately 746 watts.

Vitamin A deficiency

Lack of vitamin A causes night blindness, in which vision in dim light is impaired. Vitamin A is obtained from carrots, milk, butter and green leafy vegetables.

Liquid metal at room temperature

Mercury is the only metal that is liquid at ordinary room temperature. It is used in thermometers and barometers and has the chemical symbol Hg.

Constitution adoption date

The Constitution of India was adopted by the Constituent Assembly on 26 November 1949 and came into force on 26 January 1950, which is celebrated as Republic Day.

Article 356 President's rule

Under Article 356, the President can impose President's rule in a state if the constitutional machinery there has failed, on the Governor's report or otherwise.

Reserve Bank of India founding

The Reserve Bank of India was established on 1 April 1935 and was nationalised in 1949. It controls monetary policy and issues currency notes of denomination two rupees and above.

Chandrayaan-3 landing

India's Chandrayaan-3 mission soft-landed its Vikram lander near the Moon's south pole on 23 August 2023, making India the fourth nation to achieve a lunar soft landing.

Fundamental Duties

Fundamental Duties are listed in Article 51A of the Constitution. They were added by the 42nd Constitutional Amendment Act in 1976 on the recommendation of the Swaran Singh Committee.

First President of India

Dr Rajendra Prasad was the first President of India, serving from 1950 to 1962. He was also the first President to be re-elected for a second term.

Supreme Court article

The Supreme Court of India is established under Article 124 of the Constitution. Its judges are appointed by the President and retire at the age of 65 years.

ISRO headquarters

The Indian Space Research Organisation is headquartered at Bengaluru, Karnataka. Its main spaceport is the Satish Dhawan Space Centre at Sriharikota in Andhra Pradesh.