Surds And Indices

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SURDS

A surd is a square root which cannot be reduced to a rational number.

For example,  is not a surd.

However  is a surd.

If you use a calculator, you will see that  and we will need to round the answer correct to a few decimal places. This makes it less accurate.

If it is left as , then the answer has not been rounded, which keeps it exact.

Here are some general rules when simplifying expressions involving surds.

 

 

 

  1. am x an = am + n
  2.  

am

am – n

an

 

 

  1. (am)n = amn

 

  1. (ab)n = anbn

 

  1.  

a

n

=

an

b

bn

 

 

 

 

 

 

  1. a0 = 1

 

 

Questions

Level-I

 

1. 

(17)3.5 x (17)? = 178

A.

2.29

B.

2.75

C.

4.25

D.

4.5

 

2. 

If

a

x – 1

=

b

x – 3

, then the value of x is:

b

a

A.

1

2

B.

1

C.

2

D.

7

2

 

3. 

Given that 100.48 = x, 100.70 = y and xz = y2, then the value of z is close to:

A.

1.45

B.

1.88

C.

2.9

D.

3.7

 

4. 

If 5a = 3125, then the value of 5(a – 3) is:

A.

25

B.

125

C.

625

D.

1625

 

5. 

If 3(x – y) = 27 and 3(x + y) = 243, then x is equal to:

A.

0

B.

2

C.

4

D.

6

 

.6. 

(256)0.16 x (256)0.09 = ?

A.

4

B.

16

C.

64

D.

256.25

 

7. 

The value of [(10)150 ÷ (10)146]

A.

1000

B.

10000

C.

100000

D.

106

 

8. 

1 

+

1

+

1

= ?

1 + x(b – a) + x(c – a)

1 + x(a – b) + x(c – b)

1 + x(b – c) + x(a – c)

A.

0

B.

1

C.

xa – b – c

D.

None of these

 

9. 

(25)7.5 x (5)2.5 ÷ (125)1.5 = 5?

A.

8.5

B.

13

C.

16

D.

17.5

E.

None of these

 

10. 

(0.04)-1.5 = ?

A.

25

B.

125

C.

250

D.

625

 

 

Level-II

 

11. 

(243)n/5 x 32n + 1

= ?

9n x 3n – 1

A.

1

B.

2

C.

9

D.

3n

 

12. 

1

+

1

= ?

1 + a(n – m)

1 + a(m – n)

A.

0

B.

1

2

C.

1

D.

am + n

 

13. 

If m and n are whole numbers such that mn = 121, the value of (m – 1)n + 1 is:

A.

1

B.

10

C.

121

D.

1000

 

14. 

xb

(b + c – a)

.

xc

(c + a – b)

.

xa

(a + b – c)

= ?

xc

xa

xb

A.

xabc

B.

1

C.

xab + bc + ca

D.

xa + b + c

 

15. If 5√5 * 53 ÷ 5-3/2 = 5a+2 , the value of a is:
A. 4       
B. 5       
C. 6       
D. 8

 

16.(132)7 ×(132)? =(132)11.5.

A. 3      
B. 3.5       
C. 4    
D. 4.5

 

 

17. (ab)x−2=(ba)x−7. What is the value   of x ?

 

A. 3      
B. 4    
C. 3.5     
D. 4.5

 

 

 

18. (0.04)-2.5 = ?

 

A. 125      
B. 25      
C. 3125  
D. 625

 

 

 

 

 

Answers

Level-I

Answer:1 Option D

 

Explanation:

Let (17)3.5 x (17)x = 178.

Then, (17)3.5 + x = 178.

 3.5 + x = 8

 x = (8 – 3.5)

 x = 4.5

 

Answer:2 Option C

 

Explanation:

Given 

a

x – 1

=

b

x – 3

b

a

a

x – 1

=

a

-(x – 3)

 = 

a

(3 – x)

b

b

b

 x – 1 = 3 – x

 2x = 4

 x = 2.

 

 

Answer:3 Option C

 

Explanation:

xz = y2        10(0.48z) = 10(2 x 0.70) = 101.40

 0.48z = 1.40

 z =

140

=

35

= 2.9 (approx.)

48

12

 

Answer:4 Option A

 

Explanation:

5a = 3125        5a = 55

 a = 5.

 5(a – 3) = 5(5 – 3) = 52 = 25.

 

 

Answer:5 Option C

 

Explanation:

3x  y = 27 = 33        x – y = 3 ….(i)

3x + y = 243 = 35        x + y = 5 ….(ii)

On solving (i) and (ii), we get x = 4

 

 

Answer:6 Option A

 

Explanation:

(256)0.16 x (256)0.09 = (256)(0.16 + 0.09)

   = (256)0.25

   = (256)(25/100)

   = (256)(1/4)

   = (44)(1/4)

   = 44(1/4)

   = 41

   = 4

Answer:7 Option B

 

Explanation:

(10)150 ÷ (10)146 =

10150

10146

   = 10150 – 146

   = 104

   = 10000.

 

Answer:8 Option B

 

Explanation:

Given Exp. =

1

 + 

1

 + 

1

1 +

xb

+

xc

xa

xa

1 +

xa

+

xc

xb

xb

1 +

xb

+

xa

xc

xc

   =

xa

+

xb

+

xc

(xa + xb + xc)

(xa + xb + xc)

(xa + xb + xc)

   =

(xa + xb + xc)

(xa + xb + xc)

   = 1.

 

Answer:9 Option B

 

Explanation:

Let (25)7.5 x (5)2.5 ÷ (125)1.5 = 5x.

Then,

(52)7.5 x (5)2.5

= 5x

(53)1.5

5(2 x 7.5) x 52.5

= 5x

5(3 x 1.5)

515 x 52.5

= 5x

54.5

 5x = 5(15 + 2.5 – 4.5)

 5x = 513

 x = 13.

 

Answer:10 Option B

 

Explanation:

(0.04)-1.5 =

4

-1.5

100

   =

1

-(3/2)

25

   = (25)(3/2)

   = (52)(3/2)

   = (5)2 x (3/2)

   = 53

   = 125.

 

Level-II

 

Answer:11 Option C

 

Explanation:

Given Expression

=

(243)(n/5) x 32n + 1

9n x 3n – 1

 

=

(35)(n/5) x 32n + 1

(32)n x 3n – 1

 

=

(35 x (n/5) x 32n + 1)

(32n x 3n – 1)

 

=

3n x 32n + 1

32n x 3n – 1

 

=

3(n + 2n + 1)

3(2n + n – 1)

 

=

33n + 1

33n – 1

 

= 3(3n + 1 – 3n + 1)   = 32   = 9.

Answer:12 Option C

 

Explanation:

1

+

1

=

1

 + 

1

1 +

an

am

1 +

am

an

1 + a(n – m)

1 + a(m – n)

   =

am

+

an

(am + an)

(am + an)

   =

(am + an)

(am + an)

   = 1.

 

Answer:13 Option D

 

Explanation:

We know that 112 = 121.

Putting m = 11 and n = 2, we get:

(m – 1)n + 1 = (11 – 1)(2 + 1) = 103 = 1000.

 

Answer:14 Option B

 

Explanation:

Given Exp.

 

x(b – c)(b + c – a) . x(c – a)(c +a – b) . x(a – b)(a + b – c)

 

x(b – c)(b + c) – a(b – c)  .  x(c – a)(c + a) – b(c – a)
   .  
x(a – b)(a + b) – c(a – b)

 

x(b2 – c2 + c2 – a2 + a2 – b2)  .   xa(b – c) – b(c – a) – c(a – b)

 

= (x0 x x0)

 

= (1 x 1) = 1.

 

Answer:15 option C

 

Answer:16 

Explanation

am.an=am+n

(132)7 × (132)x = (132)11.5

=> 7 + x = 11.5

=> x = 11.5 – 7 = 4.5

 

 

Answer:17 

Explanation:

an=1a−n

(ab)x−2=(ba)x−7(ab)x−2=(ab)−(x−7)x−2=−(x−7)x−2=−x+7x−2=−x+72x=9x=92=4.5

 

Answer:18 

Explanation:

a−n=1/an

(0.04)−2.5=(1/.04)2.5=(100/4)2.5=(25)2.5=(52)2.5=(52)(5/2)=55=3125

 

 


,

Introduction to Surds

A surd is a number that cannot be expressed as a fraction of two integers. Surds are often written as roots, such as $\sqrt{2}$ or $\pi$.

Surds can be simplified by combining them into a single surd. For example, $\sqrt{2} + \sqrt{3} = \sqrt{2 \cdot 3} = \sqrt{6}$.

Surds can also be added, subtracted, multiplied, and divided. However, it is important to remember that the order of operations must be followed when performing these operations on surds.

For example, to add two surds, the surds must be in the same form. For example, $\sqrt{2} + \sqrt{3}$ can be added, but $\sqrt{2} + 3$ cannot be added.

To subtract two surds, the surds must be in the same form. For example, $\sqrt{2} – \sqrt{3}$ can be subtracted, but $\sqrt{2} – 3$ cannot be subtracted.

To multiply two surds, the product of the two surds is the square root of the product of the two numbers under the radical. For example, $\sqrt{2} \cdot \sqrt{3} = \sqrt{2 \cdot 3} = \sqrt{6}$.

To divide two surds, the quotient of the two surds is the square root of the quotient of the two numbers under the radical. For example, $\frac{\sqrt{2}}{\sqrt{3}} = \sqrt{\frac{2}{3}}$.

Surds can also be raised to powers. To raise a surd to a power, the power is applied to both the number under the radical and the radical itself. For example, $(\sqrt{2})^3 = \sqrt{2 \cdot 2 \cdot 2} = 2\sqrt{2}$.

Surds can also be taken to roots. To take the root of a surd, the root is applied to both the number under the radical and the radical itself. For example, $\sqrt[3]{\sqrt{2}} = \sqrt[3]{2}$.

Equations Involving Surds

Equations involving surds can be solved by isolating the surd on one side of the equation and then simplifying the equation. For example, to solve the equation $\sqrt{x} + 2 = 3$, we can subtract 2 from both sides of the equation to get $\sqrt{x} = 1$. Then, we can take the square root of both sides of the equation to get $x = 1$.

Indices

An index is a number that indicates how many times a base number is multiplied by itself. For example, $2^3 = 2 \cdot 2 \cdot 2 = 8$, and $3^2 = 3 \cdot 3 = 9$.

The base number is the number that is being multiplied by itself. The exponent is the number that indicates how many times the base number is multiplied by itself.

Indices can be added, subtracted, multiplied, and divided. However, it is important to remember that the order of operations must be followed when performing these operations on indices.

For example, to add two indices, the bases of the indices must be the same. For example, $2^3 + 3^2 = 8 + 9 = 17$.

To subtract two indices, the bases of the indices must be the same. For example, $2^3 – 3^2 = 8 – 9 = -1$.

To multiply two indices, the bases of the indices must be the same. For example, $2^3 \cdot 3^2 = 8 \cdot 9 = 72$.

To divide two indices, the bases of the indices must be the same. For example, $\frac{2^3}{3^2} = \frac{8}{9} = \frac{8}{9}$.

Laws of Indices

There are several laws of indices that can be used to simplify expressions involving indices. These laws are as follows:

Here are some frequently asked questions and short answers about the topic of Surds and Indices.

Sure. Here are some MCQs without mentioning the topic Surds And Indices:

  1. What is the value of $x^2 + 2x – 8$ when $x = 3$?
    (A) 1
    (B) 2
    (C) 3
    (D) 4
    (E) 5

  2. What is the value of $\frac{1}{2} + \frac{1}{4} + \frac{1}{8} + \dots + \frac{1}{2^{10}}$?
    (A) $\frac{1}{2}$
    (B) $\frac{1}{4}$
    (C) $\frac{1}{8}$
    (D) $\frac{1}{16}$
    (E) $\frac{1}{32}$

  3. What is the value of $\sqrt{25}$?
    (A) 5
    (B) 7
    (C) 10
    (D) 14
    (E) 17

  4. What is the value of $\sqrt[3]{27}$?
    (A) 3
    (B) 6
    (C) 9
    (D) 12
    (E) 18

  5. What is the value of $\log_{10} 100$?
    (A) 1
    (B) 2
    (C) 3
    (D) 4
    (E) 5

  6. What is the value of $\log_{10} 0.01$?
    (A) -2
    (B) -3
    (C) -4
    (D) -5
    (E) -6

  7. What is the value of $e^2$?
    (A) 7.38905609893065
    (B) 27.18281828459045
    (C) 72.7253908203125
    (D) 125.9765625
    (E) 218.75

  8. What is the value of $\sin 30^\circ$?
    (A) $\frac{1}{2}$
    (B) $\frac{\sqrt{3}}{2}$
    (C) $\frac{\sqrt{2}}{2}$
    (D) $\frac{1}{4}$
    (E) $\frac{1}{8}$

  9. What is the value of $\cos 60^\circ$?
    (A) $\frac{1}{2}$
    (B) $\frac{\sqrt{3}}{2}$
    (C) $\frac{\sqrt{2}}{2}$
    (D) $\frac{1}{4}$
    (E) $\frac{1}{8}$

  10. What is the value of $\tan 45^\circ$?
    (A) $\frac{1}{\sqrt{2}}$
    (B) $\sqrt{2}$
    (C) $\frac{\sqrt{3}}{2}$
    (D) $\frac{1}{2}$
    (E) 1

I hope these questions are helpful!

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