 # CAT Questions | CAT Algebra Questions | Indices and Surds

### CAT Verbal Ability

The topic Indices and Surds is a part of the Number System vertical of the Quantitative Aptitude section in the MBA entrance exam. Although we can observe from the trend that the frequency of occurrence of Indices and Surds questions in this topic has decreased, we cannot ignore this topic entirely as we can always expect 1-2 Indices and Surds questions on this topic in many MBA entrance exams.

## Exams that contains questions from Indices and Surds

Many exams ask questions on Indices and Surds. These may range from 1-2 Indices and Surds questions which are usually assigned easy to moderate level of difficulty. Hence, it is wise to cover this topic to score well.

 Exam Year No of Questions Level of Difficulty CAT 2018 1 Moderate 2018 1 Easy NMAT 2019 1 Moderate 2018 1 Easy SNAP 2018 1 Easy

## Basic concepts of Indices and Surds

### Indices:

The base ‘a’ raised to power ‘b’ is equal to the multiplication of a, b times a = a × a… × a b times. Where a is the base and b is the indices. Examples 2^1 = 2 2^2 = 2*2 = 4 2^3 = 2*2*2 = 8

### Surds:

Numbers that can be written as √a + √b, where a and b are not perfect squares and natural numbers. Hence, the numbers in the form of √5, 5√7, ……. x√y

### Rules and Properties on how to solve surds and indices problems:

 Name of the Rule Conversion Division am/ an = am-n an / bn = (a / b)n Multiplication an⋅ am = am+n an ⋅ bn = (a ⋅ b)n Power (an)m = an⋅m anm = a(nm) m√(an) = a n/m n√a = a1/n a-n = 1 / an

### Important points to Remember:

1) in surds problems Surd nx can be simplified if the factor of x is a perfect square

2)Any number raised to the power zero always equals one. (Eg: x 0 = 1)

3) The conjugate of (x√a + y√b) is (x√a – y√b)

4) If the denominator in a fraction has a surd, then rationalize the denominator by multiplying both numerator and denominator by a conjugate surd

5) Different expressions can be simplified by rationalizing the denominator and eliminating the surd

6) Every surd is an irrational number in surd questions.

## CAT Questions | Indices and Surds Question

If m and n are integers such that (√2)^19 * 3^4 * 4^2 * 9^m * 8^n = 3^n * 16^m (4√64) then m is?

1. -20

2. -24

3. -16

4. -12

Explanation:

Given, √2^19 3^4 4^2 9^m 8^n=3^n 16^m ∜64

Or 2^(19/2)×3^4×2^4×3^2m×2^3n= 3^n×2^4m×2^(6/4)

2^(19/2+4+3n)×3^(4+2m)=3^n×2^((4m+6/4) )

Comparing both sides,

n = 4+2m

19/2 +4 + 3n = 4m + 6/4

Or (19 + 8)/2 + 3(4+2m) = 4m + 3/2

27/2 + 12 + 6m = 4m + 3/2

6m -4m = 3/2 – 27/2 -12

2m = -24

Thus m = -12

If 17x = 4913, find the value of 22x-1.

a) 16

b) 32

c) 64

d) 128

17x = 4913

⇒17x = 4913

⇒17x = (17)3

⇒x = 3

Value of 22x-1 ⇒ 22.3-1⇒ 25 = 32

If 2x × 8(1/4) = 2(1/4) then find the value of x

As bases are not equal we cannot add the indices, hence first convert all the numbers with the same base.

2x × (23)(1/8) = 2(1/4)

Hint:

Law of Indices (xm)n = xmn

2x × 2(3/4) = 2(1/4)

2[x + (3/4)] = 2(1/4) If 4 (x – y) = 64 and 4 (x + y) = 1024, then find the value of x.

a. 3

b. 1

c. 6

d. 4

4 (x – y) = 64

4 (x – y) = 64 = 43

Equation 1) x – y = 3

4 (x + y) = 1024 = 45

Equation 2) x + y = 5

Solving equation (1) and (2), we get

x = 4 and y = 1

Crosscheck the answers by substituting the values of x and y in the given expression.

4 (4 – 1) = 43 = 64 and 4 (4 + 1) = 45 = 1024

Hence, the answers x = 4 and y = 1 are correct.

If a and b are whole numbers such that ab = 121, then find the value of (a – 1)b + 1

a. 0

b. 10

c. 102

d. 103

121 = 112 , hence value of a = 11 and b = 2 can be considered.

Therefore, the value of (a – 1)b + 1 = (11 – 1) 2 + 1= 103

## How to prepare for Indices and Surds Questions

Preparing for Indices and Surds will require a basic understanding of the key concepts and speedy calculation along with hard work and dedication. Here are some Level-wise preparatory guidelines to follow:

### Level – 1

1.  Learn all the basic concepts of indices and surds and their rules and properties. Take help of live lectures and lecture notes
2. Learn Speed calculation: For an effective and quick calculation, be thorough with tables till 20, memorize squares till 30, and cubes till 15. Memorize the properties of the log.
3. Practice beginner-level Indices and Surds questions. Go through MBAP CAT E Book (Concept Theory) study material and MBAP CAT E Book (Practice Questions).

### Level – 2

1. Move on to more complex surds and indices questions, attempt beginner and intermediate level mock on concepts of Indices and Surds.

2. Solve previous year CAT questions on Indices and Surds and time yourself. Do not get stuck on one question and try to solve easy questions first from surds and indices questions pdf.

3. Keep attempting mocks to check your performance.

4. Practice MBAP Topic wise Previous Year CAT paper, this can be utilized to enhance your performance.

### Level – 3

1. For advanced level preparation, start practicing Indices and Surds questions from MBAP CAT Advance E books – How to Prepare for Quantitative Aptitude for the CAT, authored by Arun Sharma.

2. Indices and Surds questions in Arun Sharma are categorized into Level of Difficulty (LOD), based upon your preparation level, start attempting 3 or 4 questions daily. Counselling Session
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