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Chapter 7: Problem 3

Find the answer mentally. What is \(15 \%\) of \(80 ?\)

Short Answer

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Step by step solution

01

Identify the Problem

Determine what 15% of 80 is.
02

Convert Percentage to Decimal

Convert 15% to a decimal by dividing by 100: \(15 \div 100 = 0.15\).
03

Multiply Decimal by the Number

Multiply the decimal result by 80: \(0.15 \times 80 = 12\).

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Key Concepts

These are the key concepts you need to understand to accurately answer the question.

converting percentages to decimals
To solve percentage problems, it's essential to convert percentages into decimals first. This makes calculations easier and more straightforward. The process is simple: divide the percentage value by 100. For instance, to convert 15% to a decimal:

\( 15 \div 100 = 0.15 \)

Doing this transformation helps to work with the percentage as a part of the whole, making the next mathematical operations seamless.
multiplication
Once you have your percentage converted into a decimal, the next step is multiplication. This is because the word 'of' in percentage problems usually indicates a multiplication operation. Here, we need to find what 15% of 80 is. After converting 15% to 0.15, we multiply it by 80:

\( 0.15 \times 80 = 12 \)

Multiplication in these problems helps us determine the proportionate part of the whole number, allowing us to easily ascertain the desired result. Using a calculator can speed up this step, though practicing it manually can enhance your arithmetic skills.
mental math
Doing calculations mentally can be quicker and more efficient in everyday situations. Practicing mental math regularly enhances your ability to work with numbers swiftly. For the given problem, let's explore simple mental math tricks:
  • First, convert 15% to a fraction: \( \frac{15}{100} = \frac{3}{20} \). This fraction is easier to work with.

  • Next, break the number down for easier multiplication. Break 80 as 4 times 20. So, \( \frac{3}{20} \times 80 \) transforms to \( \frac{3}{20} \times 4 \times 20 \).

  • Now, cancel out the 20s: 3 \times 4 = 12.

Using simple steps like these can make mental calculations less intimidating. It might take practice, but with time, you'll find yourself calculating percentages effortlessly!

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Most popular questions from this chapter

Convert the fraction to a percent. $$\frac{11}{9}$$

The rainfall at Birmingham Airport in the United Kingdom averages \(56 \mathrm{mm}\) per month. In August the amount of rain that fell was \(125 \%\) of the average monthly rainfall. How much rain fell in August?

Find the total amount in an account for an investment subject to the following conditions. Principal $$\$ 14,000$$ Annual Interest Rate $$4.5 \%$$ Time, Years $$3$$ Compounded Monthly Total Amount __________

Write the fraction in percent notation to the nearest tenth of a percent. $$\frac{3}{7}$$

At a softball game, the concession stand had 120 hot dogs and sold 84 of them. What percent was sold?
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