Chapter 2: Problem 120
(a) \(150 \%\) of 90 is what number? (b) \(6.4 \%\) of what amount is \(\$ 2.88 ?\) (a) 50 is what percent of \(40 ?\)
Short Answer
Expert verified
(a) 135 (b) 45 (c) 125%
Step by step solution
01
Understanding Percentages
To find a percentage of a number, convert the percentage to a decimal by dividing by 100, then multiply by the number.
02
Calculate 150% of 90
Convert 150% to a decimal: \(150\text{\%} = 1.50\). Now multiply by 90: \(1.50 \times 90 = 135\)
03
Setup the Equation for part (b)
Use the formula: \( \text{Percentage} \times \text{Total Amount} = \text{Given Amount} \). Set up the equation as follows: \(0.064 \times T = 2.88\), where \( T \) is the total amount.
04
Solve for the Total Amount
To find \( T \), divide both sides by 0.064: \( T = \frac{2.88}{0.064} = 45\)
05
Understanding part (c)
To find what percent one number is of another, set up a ratio and convert to a percentage by multiplying by 100.
06
Calculate the Percentage for part (c)
Set up the ratio as \( \frac{50}{40} \). Simplify the ratio: \( \frac{50}{40} = 1.25\). Convert to a percentage: \( 1.25 \times 100\text{\%} = 125\text{\%}\)
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Key Concepts
These are the key concepts you need to understand to accurately answer the question.
percent of a number
A fundamental concept in percentage calculations is finding what percent a specific number (part) is of another number (whole). We often use this to compare values.
To calculate the percent of a number:
An important point to remember is that percentages over 100% simply mean more than the whole (like 150% of 90 being greater than 90).
To calculate the percent of a number:
- Convert the percentage to a decimal by dividing the percentage by 100.
- Multiply this decimal by the given number.
An important point to remember is that percentages over 100% simply mean more than the whole (like 150% of 90 being greater than 90).
converting percentages to decimals
Converting percentages to decimals is a crucial step in many percentage calculations.
It simplifies multiplication and division. To convert:
This conversion is handy when solving word problems, such as finding what amount 6.4% of another amount equals. Here, convert 6.4% to decimal: \[6.4\text{\textpercent} = 0.064\]. Then use it in the formula:
It simplifies multiplication and division. To convert:
- Simply divide the percentage by 100.
This conversion is handy when solving word problems, such as finding what amount 6.4% of another amount equals. Here, convert 6.4% to decimal: \[6.4\text{\textpercent} = 0.064\]. Then use it in the formula:
- \text{Percentage} \times \text{Total Amount} = \text{Given Amount}
ratio and proportion
Ratios and proportions are often used in percentage calculations to understand the relation between two numbers.
A ratio is a comparison of two numbers, showing how many times one value contains another. To find what percent 50 is of 40:
A ratio is a comparison of two numbers, showing how many times one value contains another. To find what percent 50 is of 40:
- Set up a ratio: \[\frac{50}{40}\].
- Simplify the ratio: \[\frac{50}{40} = 1.25\].
- Convert to a percentage by multiplying by 100: \[1.25 \times 100 = 125\text{\textpercent}\].