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Mathematics

By converting to exponential form, find the values of :

(i) log216

(ii) log5125

(iii) log48

(iv) log927

(v) log10 (0.01)

(vi) log7 17\dfrac{1}{7}

(vii) log0.5 256

(viii) log2 0.25

Logarithms

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Answer

(i) log216 = x

⇒ 2x = 16

⇒ 2x = 24

∴ x = 4.

Hence, log216 = 4.

(ii) log5125 = x

⇒ 5x = 125

⇒ 5x = 53

∴ x = 3.

Hence, log5125 = 3.

(iii) log48 = x

⇒ 4x = 8

⇒ (22)x = 23

⇒ 22x = 23

⇒ 2x = 3

⇒ x = 32.\dfrac{3}{2}.

Hence, log48 = 32\dfrac{3}{2}.

(iv) log927 = x

⇒ 9x = 27

⇒ (32)x = 33

⇒ 32x = 33

⇒ 2x = 3

⇒ x = 32.\dfrac{3}{2}.

Hence, log927 = 32\dfrac{3}{2}.

(v) log10 (0.01) = x

⇒ 10x = 0.01

⇒ 10x = 10-2

∴ x = -2.

Hence, log10 (0.01) = -2.

(vi) log717\dfrac{1}{7} = x

⇒ 7x = 17\dfrac{1}{7}

⇒ 7x = 7-1

∴ x = -1.

Hence, log717\dfrac{1}{7} = -1.

(vii) log0.5 256 = x

⇒ (0.5)x = 256

(510)x\Big(\dfrac{5}{10}\Big)^x = (2)8

(12)x\Big(\dfrac{1}{2}\Big)^x = (2)8

⇒ (2)-x = (2)8

∴ -x = 8 ⇒ x = -8.

Hence, log0.5256 = -8.

(viii) log2 0.25 = x

⇒ 2x = 0.25

⇒ 2x = 25100\dfrac{25}{100}

⇒ 2x = 14=122\dfrac{1}{4} = \dfrac{1}{2^2}

⇒ 2x = 2-2

⇒ x = -2.

Hence, log2 0.25 = -2.

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