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Difficulty: EasyPercents and Percent Change

A software update reduced the storage space used by an application on a smartphone by 30%30\%. If the application originally used 400400 megabytes (MB\text{MB}) of storage space, how many megabytes of storage space does the application use after the update?

Answer: 280 MB

Answer

The application uses 280280 megabytes of storage space after the update.
The correct answer is 280280. The reduction in storage space is 30%30\% of the original 400400 megabytes, which is calculated as 0.30×400=1200.30 \times 400 = 120 megabytes. Subtracting this reduction from the original storage space gives 400−120=280400 - 120 = 280 megabytes. Alternatively, a reduction of 30%30\% means the remaining storage is 70%70\% of the original storage, which is 0.70×400=2800.70 \times 400 = 280 megabytes.

Step-by-Step Solution

1
Calculate the reduction in storage space.
The reduction is 120120 megabytes.
Multiply the original storage space of 400400 megabytes by the percent reduction expressed as a decimal (0.300.30).
2
Subtract the reduction from the original storage space.
The new storage space is 280280 megabytes.
Subtracting the amount of space saved (120120 megabytes) from the original space (400400 megabytes) gives the remaining space used.

Key Concept

Calculating a decreased amount after a percentage reduction.
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Topics

Percents and Percent Change

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