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Recounting theorems and formulas by heart, and knowing how and when to apply them is an essential part of CAT preparation. These formulas will help you solve question papers from previous years and mock test series that are vital to enhancing performance and quality during the exam.
Update: CAT 2020 notification has been released on July 29 by IIM Indore on official website iimcat.ac.in. Exam is scheduled to take place on November 29, 2020. Check Details on CAT 2020
So, as you begin your preparation for CAT 2020 , here's a list of important formulae you need to master. Several formulas are also given with ways in which they can be used in problems. Check CAT Quantitative Aptitude Preparation Tips
One of the simplest topics in the Quantitative section of the CAT is Logarithms, Surds, and Indices. Although there is a high number of formulae, the basic concepts are quite easy to understand and implement. There are no shortcuts to consider and there is a limited scope of the questions that can be asked. This section's accuracy in answering questions is very high and well-prepared students continue to score very well here.
Suppose X,Y > 0 and m,n are rational numbers, then,
Xm × Xn = Xm+n
X0 = 1
(Xm)n = Xmn
Xm ×Ym =(X×Y)m
Xm/Ym = (X/Y)m
X-m = 1/Xm
Suppose X and Y are positive real numbers and a,b are rational numbers, then,
Surds are irrational numbers that involve a root like . Like surds are two surds that have the same number under the radical sign. These can be added or subtracted.
In order to find must be written as , where .
When , x is defined as the logarithm of N to the base a. This is shown as:
Note: The logarithm of zero or a negative number is not defined.
When 0 < a < 1,
When a > 1,
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The more questions you answer, the stronger you get with this topic. Take a look at the formula list and comprehend the formulae. However, the best way to tackle this topic is to solve questions. From this topic, answer as many questions as you can. You will start to see that all of them are basically variations of the same few themes that are mentioned in the formula list.
Arrangement: n items may be arranged in n! ways.
Permutation: This is a way of choosing and arranging r items out of a set n objects a
Combination: This is a way of choosing and r items out of n, where the arrangement does not matter. It is represented as
Choosing r items from n is similar to choosing (n-r) items out of n.
The total number of choices that can be made from n distinct items is represented as
Partitioning : The number of ways to partition n identical items in r different slots is shown as .
The number of ways to partition n identical items in r different slots such that every slot receive a minimum of 1 is shown as .
The number of ways to partition n dissimilar items in r distinct slots is given as .
The number of ways to partition n dissimilar items in r different slots such that the arrangement matter is given as .
Arranging with repetitions
When x items from n items get repeated, the number of ways of arranging n items is n! ways. Suppose a, b, and c items are x! n! that are related within n items, then they can be arranged in a! b! c! ways.
Rank of a word
To obtain the rank of a word in the alphabetical list of the word’s permutations, begin with alphabetical arrangement of n letters. Suppose there are x letter greater than the first letter of the word, there will be a minimum of x* (n-1)! words above the word.
Eliminate the first affixed letter from the set. If there are y letters above the second letter, then will be y* (n-2)! words higher before the word and so on.
Therefore, the rank of the word is x* (n-1)! + y* (n-2)! … +!
The number of positive integral solutions to , where .
The number of non-negative integral solutions to , where .
The number of ways to arrange n items around a circle are 1 for n = 1,2 and (n-1)! for
Suppose it is a bracelet or necklace that could be flipped over, the possibilities would be (n-1)!/2.
When n different items are arranged, the number of which they could be arranged such that they do not take up their intended place is .
Some of the simplest problems in the quantitative section are those of Simple Interest (S.I) and Compound Interest (C.I) The number of concepts in these topics is small, and most of the problems could be solved by direct application of the formulae. The principal and the interest (that occurs every period) remain constant in Simple Interest. In Compound Interest, after each compounding period, the interest received over the duration is rolled back to the current principal.
Thus, the principal and the interest change after each compounding period over a period of time. With a positive interest rate and time period (>1 year) for the same principal, the compound interest on the loan is always higher than the simple interest.
Amount (A) = Principal (P) + Interest (I)
The Simple Interest (I) that has occurred over a period of time (T) for a rate of interest per annum R is, .
If money is borrowed at Compound Interest (I) for N number of years, the Amount to be paid is, . The Interest is A-P, i.e, .
When the interest is compounded half yearly, the Amount is, .
When the interest is compounded quarterly, the Amount is .
Simple Interest and Compound Interest
If the rate of interest is R1% for the first year, R2% for the second year and R3% for the third year, the Amount is .
If there is a difference between C.I and S.I at the same interest rate for a certain amount, then .
If the interest is compounded yearly but the time is in fraction form, then, assume that . Then, the Amount is, .
Suppose R is the rate per annum, the current worth of Rs. K that is due in N years will be given as,
Current worth = .
The amount paid to buy an item, or the cost of making an item is known as Cost Price (C.P). The price at which a commodity is sold is called the Selling Price (S.P). The price the article is marked with is called Marked Price (M.P).
When S.P > C.P, Profit (P) = S.P - C.P.
When C.P > S.P, Loss (L) = C.P - S.P.
%Profit = Profit/C.P x 100
%Loss = Loss/C.P x 100
Discount = M.P - S.P
(Note: when do discount is provided, M.P = S.P)
%Discount = Discount/M.P x 100
The total rise in price owing to two subsequent increased of X% and Y% is expressed as .
Suppose two items are sold at the same price Rs. X, one with a profit of P% and the other at a loss of P%. There will then be an overall loss of . The absolute loss value will be .
Geometry is one amongst the most difficult sections without preparation and one of the simplest with preparation. This section will take a lot of time to master, with so many formulas to learn and remember. Learn and recall formulas and try visualizing and solving as many formula-related questions as you can.
|Quadrant I||X is Positive||Y is Positive|
|Quadrant II||X is Negative||Y is Positive|
|Quadrant III||X is Negative||Y is Negative|
|Quadrant IV||X is Positive||Y is Negative|
In a right-angled triangle ABC, .
When AD is the media to side BC is a triangle ABC, .
The line that connects the midpoint of any two sides of a triangle is seen to be parallel to the third side. It is also half the length of the third side.
When X is the midpoint of CA and y the midpoint of CB, XY will be parallel to AB and XY = ½ * AB.
Basic Proportionality Theorem
When a line is parallel to one side of a triangle and it intersects the other two sides at two points, it splits the two sides into the ratio of the respective sides.
Suppose in a triangle ABC, D and E are the points that lie on AB and BC.
Then, AD/DB = EC/BE.
Angle Bisector Theorem
When PS is the angle bisector for angle P, RS/QS = PR/RS.
When x is the side of an equilateral traingle,
When a, b, and c are the lengths of sides BC, AC, and AB respectively,
Direct Common Tangents
Transverse Common Tangent
Areas of Geometrical Figures
Triangle = ½ * base * height
Rectangle = length * width
Trapezoid = ½ * sum of bases * height
Parallelogram = base * height
Rhombus = ½ * product of diagonals
Kite = ½ * product of diagonals
Volumes of Solids
Cuboid = length * base * height
Prism = area of base * height
Pyramid = ⅓ * area of base * height
Cone Frustum =
Total Surface Area of Solids
Prism = 2 * base area + base perimeter * height
Cuboid = 2(lh + bh + lb)
Pyramid = ½ * perimeter of base * slant height + area of base
Cone (when l is the slant height) =
Cone Frustum =
A ratio can be represented either as fraction a/b or using the a: b notation. In each of these representations, 'a' is the antecedent and ′b′ is called the consequent. The amounts of the products should be of the same character for a ratio to be described. A ratio does not have to be positive. If we deal with quantities of products, however, their ratios will be positive.
A ratio remains the same if the same non-zero number multiplies or splits both the previous and the consequent.
You can compare two ratios in their fraction notation, just as we compare real numbers.
When a, b, and x are positive,
When two ratios a/b and c/d are equal,
For all real p, q, r, s such that pa+qb≠0 and rc+sd≠0,
The duplicate ratio of a:b is
The sub-duplicate ratio of a:b is
The triplicate ratio of a:b is
The sub-triplicate ratio of a:b is
The most important topic in the quantitative section is Number Systems. It is a rather vast topic and from this segment, a large number of questions appear in CAT each year. Knowing basic tricks such as rules of divisibility, HCF and LCM, prime number and remaining theorems will help significantly boost the ranking.
The concept is very easy and the students should be interested in this subject. Some simple formulae and definitions are convenient. Techniques such as the elimination of options and the assumption of value can help to quickly resolve questions from this subject.
Sum of Roots = -b/a
Product of Roots = c/a
Mixtures and Alligations
This is the rule that helps one to find the ratio in which two or more ingredients must be combined at the specified price to produce a mixture of the desired amount.
The expense of a mixture unit quantity is called the mean price.
If there are two ingredients combined then, (Quantity of cheaper / Quantity of dearer) = (C.P. of dearer – Mean Price / Mean price – C.P. of cheaper)
The Law of Demorgan is the basic and most important formulation for sets, defined as,
(A ∩ B) ‘ = A’ U B’ and (A U B)’ = A’ ∩ B’
The relation, R⊂A×AR⊂A×A, is known as:
Reflexive Relation: When a R a ∀∀ a ∈∈ A.
Symmetric Relation: When aRb, bRa ∀∀ a, b ∈∈ A.
Transitive Relation: When aRb, bRc, aRc ∀∀ a, b, c ∈∈ A.
When any relation R is symmetric, reflexive, and transitive in a specific set A, that relation is called an equivalence relation.
Formulas for Probability
If we do an experiment, then the sample space is called the set S of all potential outcomes.
The event is called any subset of a sample space.
Let S be the sample and E be an event. P is the probability of occurrence of an event.
Thus, P(E) =n(E) / n(S).
In order to find out what percentage of x is y: y/x × 100,
Increase N by S % = N( 1+ S/100 )
Decrease N by S % = N (1 – S/100)
Distance = Speed x Time
Time = Distance/Speed
Average Speed = Total Distance Travelled/Total Time Taken
Suppose A can do work in n days, then A’s 1 day’s work = 1/n
When A’s 1 day’s work =1/n, A can complete the work in n days.
Arithmetic Mean =
Nth term =
Geometric Mean =
Nth term =
Harmonic Mean =