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15 Flashcards in this deck.
A ratio is a relationship between two or more quantities, indicating how many times one value contains or is contained within the other. Ratios are typically expressed in the form $a:b$ or $\frac{a}{b}$, where $a$ and $b$ are the quantities being compared.
For example, if there are 2 apples and 3 oranges, the ratio of apples to oranges is $2:3$. This means that for every 2 apples, there are 3 oranges.
Equivalent ratios are ratios that express the same relationship between quantities, even if the actual numbers differ. To find equivalent ratios, you can multiply or divide both terms of the ratio by the same non-zero number.
For instance, the ratio $2:3$ is equivalent to $4:6$, $6:9$, and so on. These ratios all maintain the same relationship between the quantities.
Simplifying a ratio involves reducing the ratio to its simplest form by dividing both terms by their greatest common divisor (GCD). This makes it easier to work with ratios in problem-solving.
Consider the ratio $8:12$. The GCD of 8 and 12 is 4. Dividing both terms by 4, the simplified ratio is $2:3$.
Sharing amounts according to a given ratio involves dividing a total quantity into parts that are proportional to the ratio provided. The general steps include:
For example, to share \$120 in the ratio $3:2$, you first add the ratio terms: $3 + 2 = 5$ parts. Then, each part is \$120 divided by 5, which is \$24. Therefore, the shares are:
Understanding how to share amounts in a given ratio is applicable in various real-life scenarios, such as:
Ratio problems can often be solved using algebraic equations. Let’s consider a problem where you need to share \$150 in the ratio $5:3$.
Let the shares be $5x$ and $3x$. According to the problem:
$$5x + 3x = 150$$ $$8x = 150$$ $$x = \frac{150}{8} = 18.75$$Therefore, the shares are:
Ratios and proportions are closely related concepts. A proportion states that two ratios are equal. Solving proportions often involves finding the missing term by cross-multiplying.
For example, to solve the proportion $\frac{a}{b} = \frac{c}{d}$ for $d$, you can cross-multiply:
$$a \times d = b \times c$$ $$d = \frac{b \times c}{a}$$Consider a recipe that requires ingredients in the ratio $2:3:5$ for flour, sugar, and butter. If you need to make a larger batch using 10 cups of flour, you can determine the required amounts of sugar and butter.
First, determine the scaling factor:
$$2x = 10 \Rightarrow x = \frac{10}{2} = 5$$Then, calculate the other ingredients:
Common misconceptions when working with ratios include:
Clarifying these misconceptions is vital for accurately solving ratio problems.
Ratios can also be applied in mixture problems, where different substances are combined in specific ratios. The method of alligation is a technique used to solve such problems by finding the mean or weighted average.
For example, blending two solutions with different concentrations in a specific ratio can determine the concentration of the resulting mixture.
Aspect | Ratios | Proportions |
---|---|---|
Definition | Comparative relationship between two or more quantities. | Statement that two ratios are equal. |
Notation | $a:b$, $\frac{a}{b}$ | $\frac{a}{b} = \frac{c}{d}$ |
Purpose | To compare quantities and determine relative sizes. | To establish equality between two ratios and solve for unknowns. |
Applications | Dividing resources, recipe adjustments, scaling models. | Solving for missing terms in equal relationships, mixture problems. |
Key Operations | Simplification, finding equivalent ratios, scaling. | Cross-multiplication, solving equations. |
Use the acronym "PART" to remember the steps: P for Parts (identify the ratio terms), A for Add (sum the parts), R for Ratio (divide the total by the sum), and T for Multiply (apply to each ratio term). Creating visual aids like ratio tables can also help in understanding and solving problems more effectively, ensuring accuracy during exams.
Ratios have been used since ancient civilizations for tasks like land division and trade. The concept of the Golden Ratio, approximately 1.618, appears in nature, art, and architecture, exemplifying aesthetically pleasing proportions. Additionally, ratios play a crucial role in financial models, helping businesses determine profit-sharing and investment returns.
One frequent error is confusing ratios with fractions, leading to incorrect simplifications. For example, interpreting a ratio of $2:4$ as $2 \div 4 = 0.5$ instead of recognizing it simplifies to $1:2$. Another mistake is not accounting for all parts of the ratio when dividing a total amount, which can result in unequal shares contrary to the given proportions.