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Answer:

The new price of the professional sound system is 0.85 d dollars.

Step-by-step explanation:

If the original price was d dollars.

Then, the price of a professional sound system was reduced by 15%.

then, we solve the problem as follows:

New price=(original price)-15% of (original price)[tex]=d-\frac{15}{100}\cdot d[/tex]

=[tex]\frac{100\cdot d-15 \cdot d}{100}[/tex]=[tex]\frac{85d}{100}[/tex]

Therefore, the new price of the sound system is, [tex]\frac{85d}{100}[/tex] dollars or 0.85 d dollars.


The original price of professional sound system is [tex]\boxed{\$\ 0.85\text{d}}[/tex].

Further explanation:

Given:

The original price of sound system is [tex]d\text{ dollars}[/tex].

The price of professional sound system is reduced by [tex]15\%[/tex].

The objective is to find the new price of that professional sound system.

Percentage:

Percentage can be written in the ratio that is expressed as a fraction of [tex]100[/tex].

Now, convert [tex]15\%[/tex] into decimals as follows:

[tex]\begin{aligned}15\%&=\dfrac{15}{100}\\&=0.015\end{aligned}[/tex]  

Let the original price of the sound system be [tex]100[/tex] dollars. Now, its price was decreased by [tex]15\%[/tex] .

The amount by which the price is reduced is calculated as follows:

[tex]\dfrac{15}{100}\times100=15[/tex]

This implies that the price is reduced by [tex]\$15[/tex].

Then its new price is calculated as follows:

[tex]100-15=85[/tex]

Given that the original price of the sound system was [tex]d[/tex] dollars.

Now, its price was reduced by [tex]15\%[/tex], means the price of sound system was reduced by [tex]15\%[/tex] of its original price.

The new price is calculated if the reduced price is subtracted from the original price as shown below:

[tex]\begin{aligned}d-0.15d&=d(1-0.15)\\&=0.85d\end{aligned}[/tex]  

Now convert [tex]0.85d[/tex] into fractions as follows:

[tex]\boxed{0.85d=\dfrac{85d}{100}}[/tex]

Therefore, the new price of professional sound system is [tex]\boxed{\$\ 0.85\text{d}}[/tex].

Learn more:

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2. A problem on scientific notation of numbers https://brainly.com/question/4736384

Answer details:

Grade: Middle school

Subject: Mathematics

Chapter: Percentage

Keywords: Price, professional, sound system, reduced, 15%, new, price, original price, d, dollars, percentage, decreased, decimals.