Logarithmic functions > Logarithms
12345Logarithms

Solutions to the exercises

Exercise 1
a

4 log ( 64 ) = 3

b

4 log ( 64 ) 4.3 (using the calculator)

c

1 3 log ( 60 ) 3.7 (using the calculator)

d

1 3 log ( 81 ) -4

e

1 3 log ( 1 81 ) = 4

f

0.1 log ( ) = -6

Exercise 2
a

6 1 = 6 and 6 2 = 36 , so 1 < 6 log ( 30 ) < 2 .

b

3 3 = 27 and 3 4 = 81 , so 3 < 3 log ( 70 ) < 4 .

c

( 1 2 ) -3 = 8 and ( 1 2 ) -4 = 16 , so -4 < 1 2 log ( 10 ) < -3 .

d

( 1 3 ) 4 0.012 and ( 1 3 ) 5 0.004 , so 4 < 1 3 log ( 0.01 ) < 5 .

Exercise 3
a

5.026

b

-8.399

c

-3.597

d

0.306

Exercise 4
a

10 x = 0.01 , so x = 10 log ( 0.01 ) = -2 .

b

2 x = 60 , so x = 2 log ( 60 ) 5.9 .

c

0.8 t = 0.5 , so t = 0.8 log ( 0.5 ) 3.1 .

Exercise 5

2 t = 3 gives you t = 2 log ( 3 ) 1.58 hours.

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