RRB Group D key terms

The smallest positive number that is a multiple of two or more given numbers. For example, the LCM of 4 and 6 is 12, because 12 is the first number that both divide exactly.

The largest positive number that divides two or more given numbers exactly, leaving no remainder. For instance, the HCF of 12 and 18 is 6.

A way of expressing a number as a part of 100, written with the symbol %. For instance, 45% means 45 out of every 100, which is the fraction 45/100.

Interest calculated only on the original principal for the whole period, using the formula SI = P × R × T / 100, where R is the yearly rate and T the time in years.

Interest calculated on the principal plus any interest already earned, so the amount grows in each period. The formula for the total amount is A = P(1 + R/100)^T.

A ratio compares two quantities of the same kind, such as 3:2. A proportion states that two ratios are equal, for example 3:2 = 6:4.

The sum of a set of values divided by the number of values in the set. It gives one number that stands for the middle value of the whole group.

In a right-angled triangle, the square of the longest side equals the sum of the squares of the other two sides, written as a² + b² = c².

The amount of flat space enclosed inside a circle, found by multiplying pi (about 3.14) by the square of the radius, written as A = πr².

A rule for the order of operations in a calculation: Brackets, Of, Division, Multiplication, Addition, Subtraction. Work through these steps in that order of priority.

A question that asks you to find the same relationship between two items as exists between a given pair, such as 'Doctor is to Hospital as Teacher is to School'.

A sequence of numbers that follows a hidden rule. You must work out the pattern and then supply the next number or the missing one.

A puzzle in which words or letters are replaced by other letters, numbers or symbols using a fixed rule, and you must apply that same rule to find the answer.

Reasoning questions about family relationships, where you trace how people are related to each other using clues such as 'A is the son of B'.

Problems that track a person's movement in terms of north, south, east and west, and then ask for the final direction or the shortest distance from the starting point.

A logical question that gives two or more statements assumed to be true, from which you decide which conclusions definitely follow, whatever the real-world facts may be.

The figure produced by flipping a shape across a vertical line, so that left and right are swapped while top and bottom stay exactly as they were.

A diagram of overlapping circles that shows how groups or sets share members. It is often used to solve questions about items belonging to more than one category.

Three rules describing how objects move: an object stays at rest or in steady motion unless a force acts; force equals mass times acceleration; every action has an equal and opposite reaction.

The process by which green plants use sunlight, water and carbon dioxide, with the help of the green pigment chlorophyll, to make food and release oxygen.

A rule stating that the current through a conductor is directly proportional to the voltage across it and inversely proportional to its resistance, written as V = IR.

A scale from 0 to 14 that measures how acidic or basic a solution is. Values below 7 are acidic, 7 is neutral, and values above 7 are basic.

Organic substances needed in small amounts for normal health and growth. Each vitamin, such as A, B, C, D or K, prevents particular deficiency diseases.

The standard system of measurement units used in science, including the metre for length, the kilogram for mass, the second for time and the ampere for electric current.

The bending of light when it passes from one transparent medium into another of different optical density, for example from air into water or glass.

The smallest structural and functional unit of a living organism, bounded by a membrane and containing cytoplasm and usually a nucleus.

The combining capacity of an element or radical, showing how many hydrogen atoms it can combine with or replace, such as 1 for sodium and 2 for calcium.

The supreme law of the country, adopted on 26 November 1949 and enforced on 26 January 1950, which sets out the structure of government and the rights of citizens.

Basic rights guaranteed to every citizen by Part III of the Indian Constitution, including equality, freedom of speech, and protection from exploitation, which can be enforced in court.

The national legislature made up of the President, the Rajya Sabha (Council of States) and the Lok Sabha (House of the People), which frames the laws of the country.

The system of local self-government in villages, set up under the 73rd Constitutional Amendment, with elected bodies at village, block and district levels.

A single indirect tax on the supply of goods and services across India, introduced on 1 July 2017 to replace many earlier separate taxes.

The central bank of India, which issues currency, controls the money supply, regulates commercial banks and manages the country's foreign exchange reserves.

The Indian Space Research Organisation, the national space agency, which builds and launches satellites and carries out missions such as Chandrayaan and Mangalyaan.

A major international multi-sport event held every four years, in Summer and Winter editions, where athletes from many countries compete for gold, silver and bronze medals.