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iGCSE (2021 Edition)

20.05 Logarithms (Extended)

Worksheet
Logarithms
1

Rewrite each of the following equations in logarithmic form:

a

5^{2} = 25

b

3^{x} = 81

c

3^{1} = 3

d

2^{0} = 1

e

4.4^{0} = 1

f

25^{1.5} = 125

g

4^{\frac{5}{2}} = 32

h

4^{ - 2 } = 0.0625

i

4^{ - 3 } = \dfrac{1}{64}

j

x^{1.5} = 64

k

4^{m} = 9

l

5^{m} = q

m

w = h^{q}

n

\dfrac{1}{m^{ - j }} = n

2

Rewrite each of the following equations in logarithmic form:

a

10^{2} = 100

b

10^{ - 2 } = \dfrac{1}{100}

c

10^{\frac{1}{2}} = \sqrt{10}

d

10^{ - \frac{1}{2} } = \dfrac{1}{\sqrt{10}}

3

Rewrite each of the following equations in exponential form:

a

\log_{4} 16 = 2

b

\log_{5} 5 = 1

c

\log_{8} 1 = 0

d

\log_{2} 0.125 = - 3

e

\log_{3} \dfrac{1}{3} = - 1

f

\log_{5.8} 33.64 = 2

g

\log_{\frac{1}{3}} 9 = - 2

h

\log_{x} 32= 5

i

\log_{8} x = 6

j

\log_{g} 5 = 3

k

\log_{7} m = 40

l

\log_{y} k = u

m

\log_{r} p=y

4

Rewrite each of the following equations in exponential form:

a

\log_{10} 10\,000 = 4

b

\log_{10} \left(\sqrt{10}\right) = \dfrac{1}{2}

c

\log \left(\dfrac{1}{10\,000}\right) = - 4

d

\log \left(\dfrac{1}{\sqrt{10}}\right) = -\dfrac{1}{2}

5

True or false: The equation 4 \left(1.09\right)^{x} = 20 is equivalent to x = \log_{1.09} 5.

Evaluating logarithms
6

For each of the following equations:

i

Rewrite the equation in logarithmic form.

ii

Find the value of x, correct to two decimal places.

a

10^{x} = 820

b

10^{x} = 0.0002

c

10^{x} = \dfrac{13}{50}

d

10^{x} = 14\,000

7

For each of the following numbers:

i

Express the number as a power of 10.

ii

Hence state the base ten logarithm of the number.

a

1\,000\,000

b

0.000\,001

c

1

d

\dfrac{1}{10}

8

Evaluate the following logarithmic expressions without the use of technology:

a

\log_{2} 64

b

\log_{2} \left(\dfrac{1}{2}\right)

c

\log_{5} 0.04

d

\log_{7} 1

e

\log_{1.1} 1.21

f

\log_{0.5} 4

g

\log_{\frac{1}{5}} 25

h

\log_{27} 3

i

\log_{2} \left(\dfrac{1}{16}\right)

9
a

Find the value of the following:

i
5^0
ii
\left( \dfrac{3}{4} \right)^0
iii
12^0
iv
0.5^0
b

The logarithm, with any base, of what number is equal to zero?

10

In order to estimate \log_{10}90 without a calculator:

a

Find \log_{10}10.

b

Find \log_{10}100.

c

Between which two consecutive integers would you expect \log_{10}90 to lie?

11

For each of the following common logarithms:

i

Between which two consecutive integers would you expect the logarithm to lie?

ii

Find the value of the logarithm, correct to four decimal places.

a
\log 8892
b
\log 0.053
c
\log 534
d
\log 0.776
12

Evaluate the following logarithmic expressions, correct to two decimal places:

a

\log_{10} 40

b

\log_{10} 7692

c

\log_{10} 0.005\,79

d

\log_{10} 8

e

\log_{3} 8

f

\log_{6} 20

g

\log_{0.5} 7

h

\log_{0.3} 15

i

- \log_{2} 23

j

5 \log_{4} 17

k

\log_{5} \left( 20^{2} \times \dfrac{3}{43}\right)

l

\log_{3} 6 + 2 \log_{3} 10 - 5 \log_{3} 15

13

Find the number such that the base ten logarithm of the number is 2.5. Round your answer to two decimal places.

14

Find the number such that the base ten logarithm of the number is - 1.2. Round your answer to three decimal places.

15

Find the number, if the logarithm of the number is 0.

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Outcomes

0607E3.10A

Logarithmic function as the inverse of the exponential function y = a^x equivalent to x = log_a y. Solution to a^x = b as x = log b/log a.

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