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secondary 3 | A Maths
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LYY
LYY

secondary 3 chevron_right A Maths chevron_right Singapore

I need help with (ii)

I'm stuck at the equation lg(0.001/Io)∧10 = 90. Where do I go from here?

Date Posted: 2 years ago
Views: 193
J
J
2 years ago
Alternative way (based on your approach) :


Sub L = 90, I = 10⁻³ ,

90 = 10lg (10⁻³ / I₀)

90 = lg(10⁻³ / I₀)¹⁰

Raise 90 to the power/index

10⁹⁰ = (10⁻³ / I₀)¹⁰

(10⁹)¹⁰ = (10⁻³ / I₀)¹⁰

The two single terms have the same power/index so compare the bases.


10⁹ = 10⁻³ / I₀
I₀ = 10⁻³ / 10⁹
I₀ = 10⁻³⁻⁹
I₀ = 10⁻¹² or 1 / 10¹²

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Thaddeus
Thaddeus's answer
18 answers (A Helpful Person)
lg is base 10 log
Sub L = 90, I = 10⁻³ ,

90 = 10lg (10⁻³ / I₀)
9 = lg (10⁻³ / I₀)
Raise the base to the power/index,
10⁹ = 10⁻³ / I₀
I₀ = 10⁻³ / 10⁹
I₀ = 10⁻³⁻⁹
I₀ = 10⁻¹² or 1 / 10¹²
done {{ upvoteCount }} Upvotes
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J
J's answer
1022 answers (A Helpful Person)