Logarithms 2011 Worksheet

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MATHEMATICS : LOGARITHMS : WORKSHEET-I

Multiple Choice Questions with one or more than one correct option 1.

Which of the following when simplified reduces to an integer ? (A)

2.

2 log 6 log12 + log 3

Let N =

log5 16 − log5 4 (C) log5 128

log 32 (B) log 4

1

+ log log abc bc

1 ca

(B) a prime number (D) an integer

+ log abc

(A) 1/2

1 ab

abc

has the value equal to:

(B) 1 1

4.

−2

log3 135 log3 5 − . Then N is : log15 3 log405 3

(A) a natural number (C) a rational number 3.

 1 (D) log1/4    16 

log5 9 Let, N = 81 + 3 409

(A) 0

3 log

6

3



. 

( 7)

(C) 2 2 log25 7

(D) 4

 − 125log 25 6  then log N has the value = 2 

(B) 1

(C) − 1

(D) none

5.

The number of solution of the equation, log(− 2x) = 2 log (x + 1) is : (A) zero (B) 1 (C) 2 (D) none

6.

If a log b x − 5 x logb a + 6 = 0, where a > 0, b > 0 & ab≠1, then the value of x equals:

(

)

2

(A) 2logb a 7.

(B) 3loga b

The expression, logp logp

(D) a logb 3

(C) b loga 2

p p p

...... p p where p ≥ 2, p ∈ N, when simplified is : 14 4244 3 n radical sign

(A) independent of p, but dependent on n (B) independent of n, but dependent of p (C) dependent on both p & n (D) negative. 8.

If 5 x log2 3 + 3log 2 x = 162 then logarithm of x to the base 4 has the value equal to (A) 2 (B) 1 (C) − 1 (D) 3/2

9.

If a = logx yz, b = logy zx & c = logz xy where x, y, z are positive reals not equal to unity, then abc − a − b − c is equal to : (A) 2 (B) 1 (C) − 1 (D) zero

10.

If log1/3

3x − 1 is less than unity then x must lie in the interval : x+2

(A) (− ∞,− 2)∪ (58 , ∞) (B) (−2, 58) ASSIGNMENT - LOG

(C) (− ∞,− 2)∪ ( 13 ,

5 8

)

(D) (−2, 13) IIT - 2011

11.

12.

The equation logx2 16 + log2x64 = 3 has : (A) one irrational solution (C) two real solutions

(B) no prime solution (D) one integral solution

Assuming all logarithms to be well defined, the value of 1 1 1 equals : + + logbc2 abc log ca 2 abc logab 2 abc

(A) 3

(B) 2

(C)

1 2

(D)

3 2

13.

If a = logx yz, b = logy zx & c = logz xy where x, y, z are positive reals not equal to unity, then abc − a − b − c is equal to : (A) 2 (B) 1 (C) − 1 (D) zero

14.

If 3 2 log3 x − 2 x − 3 = 0, then the number of values of 'x' satisfying the equation is (A) zero (B) 1 (C) 2 (D) more than 2

15.

= 1 is : Number of real solution(s) of the equation x − 3 (A) exactly four (B) exactly three (C) exactly two (D) exactly one

16.

If log1/5 (2x − 4) < log1/5 (x + 3) then : (A) x < 7 (B) 2 < x < 7

3 x 2 − 10 x + 3

(C) x > 7

(D) none

17.

The value(s) of 'b' for which the equation, 2 log1/25 (bx + 28) = − log5 (12 − 4x − x2) has coincident roots, is/are : (A) b = − 12 (B) b = 4 (C) b = 4 or − 12 (D) b = − 4 or 12

18.

The solution set of the equation, 3 log10 x + 2 log10 (A) {10, 10 2}

19.

(B) {10, 103}

If 0º < x < 90º & cos x = (A) 0

ASSIGNMENT - LOG

3 10

(B) 1

1 = 2 is : x

(C) {10, 104}

(D) {10, 102, 104}

then the value of, log10 sinx + log10cos x + log10 tan x is : (C) − 1

(D) none

IIT - 2011

MATHEMATICS : LOGARITHMS : WORKSHEET-I

ANSWERS 1. A,D

2. A,B,C,D

3. B

4. A

5. B

6. B,C

7. A,D

8. D

9. A

10. A

11. C

12. A

13. A

14. B

15. B

16. C

17. B

18. C

19. C

ASSIGNMENT - LOG

IIT - 2011

MATHEMATICS : LOGARITHMS : WORKSHEET-II

State whether True or False with justification 1.

log4 18 is not a rational number.

2.

State whether True or False. log3x . log4x . log5x = log3x . log4x + log4x . log5x + log5x . log3x has two real solutions.

Fill in the blanks with suitable values 1.

Solution set of the equation, log 102 x + log10x2 = log 102 2 − 1 is ______ .

2.

Solve for x . log4 (log2x) + log2 (log4x) = 2 is ______ .

3.

If log147 = a & log14 5 = b, then log35 28 can be expressed in terms of 'a' and 'b' as______ .

4.

Given, logax = α ; logbx = β ; logcx = γ & logdx = δ (x ≠ 1), then logabcd x has the value equal to ______ .

5.

1 log 2

6.

log 3 log 2 log 3 81 has the value equal to ______ .

7.

The expression (0.05)

5

 π  5

sin   . log

5 simplifies to ______ .

sin π5

log

20

( 0. 1 )

is a perfect square of the natural number ______

(where

0.1 denotes 0.111111 ..... ∞)

(

)

2+ 8 =

1 . Then the value of 1000 x is equal to _____ . 3

8.

If logx log18

9.

The solution set of the system of equations, log3x + log3y = 2 + log32 and log27(x + y) =

2 is ______ . 3

10.

If log3 log4 log32 (x − 3) vanishes, then x can be equal to ______ or ______ .

11.

The ordered pair (x, y) satisfying simultaneously the system of equations ; logx log3 logx y = 0 and logy 27 = 1 is ______ , ______ . loga a 2 − 1 . log12/ a a 2 − 1

If

13.

Which is greater, 2 log12 145 or 15 .

14.

Solve for x , y :

(

)

loga 2 a − 1 . log3 a 6 a − 1 2

ASSIGNMENT - LOG

2

=

1 then the value of 'a' is equal to ______ . 2

12.

log100 x + y =

1 2 IIT - 2011

log10 y − log10 x = log100 4 .  5 x

15.

Solve the equation, log52 x + log5x   = 1 .

16.

 > 0 . Solve , log0.2 log6  2  x + 1

17.

Find the solution set of the equation, (log5 x)2 + log5x

 x2 − x 

5 =1. x

MATHEMATICS : LOGARITHMS : WORKSHEET-II

ANSWERS

1. True

1 1 , 20 5

2. True

2−a

2. x = 16

3. a + b

4.

5. 2

6. 1

7. 9

8. 125

9. (6 , 3) & (3 , 6) ]

10.

13 x = − 10 , y = 20

14. 1 , 5 ,

1.

ASSIGNMENT - LOG

28 or 12 ] 9

 

1  25 

11..a =

5 +1 2

α

−1

1 + β + γ −1 + δ −1 −1

12. 2 log12 145

15. (− ∞ , − 1)

IIT - 2011

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