Mathematics Grade 8 15 min

Compare ratios: word problem

Compare ratios: word problem

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1

Introduction & Learning Objectives

Learning Objectives Identify and extract relevant quantities to form ratios from word problems. Express ratios in various forms (fraction, colon, 'to') and convert them for comparison. Calculate and use unit rates to compare different ratios. Find common denominators to compare ratios expressed as fractions. Solve real-world problems by comparing two or more ratios. Interpret the meaning of ratio comparisons within the context of the original word problem. Ever wonder which deal is truly better at the grocery store, or which athlete has a stronger performance? 🍎🛒 Comparing ratios helps us answer these questions! In this lesson, you'll learn how to take information from word problems, turn it into ratios, and then use different strategies to compare those ra...
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Key Concepts & Vocabulary

TermDefinitionExample RatioA comparison of two quantities by division. It shows how much of one quantity there is compared to another.If there are 3 red apples and 5 green apples, the ratio of red to green apples is 3:5, 3 to 5, or 3/5. Equivalent RatiosRatios that represent the same relationship between two quantities. They can be obtained by multiplying or dividing both parts of a ratio by the same non-zero number.The ratio 1:2 is equivalent to 2:4 because (1x2):(2x2) = 2:4. Unit RateA ratio where the second quantity (denominator) is 1. It tells you 'how much per one' of something.If you drive 120 miles in 2 hours, your unit rate (speed) is 60 miles per 1 hour (60 mph). ProportionAn equation that states that two ratios are equal. It's often used to find an unknown quantit...
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Core Formulas

Expressing Ratios A ratio comparing quantity 'a' to quantity 'b' can be written as $a:b$, $a \text{ to } b$, or $\frac{a}{b}$. Choose the form that is most convenient for the problem, often the fraction form $\frac{a}{b}$ for comparisons. Finding Equivalent Ratios To find an equivalent ratio, multiply or divide both parts of the ratio by the same non-zero number $k$: $(a \times k) : (b \times k)$ or $(a \div k) : (b \div k)$. This rule is essential for simplifying ratios or for converting them to a common denominator or unit rate. Comparing Ratios using Unit Rates To compare two ratios, convert each ratio into its unit rate by dividing the first quantity by the second quantity. Then, compare the resulting unit rates. This method is particularly us...

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Sample Practice Questions

Challenging
A school's basketball team scored 45 points in the first half of a game (20 minutes) and 55 points in the second half (20 minutes). A rival team scored 95 points over their entire 40-minute game. Which team had a higher average scoring rate for their entire game?
A.The first team
B.The rival team
C.Their scoring rates were identical.
D.The team that scored more in the second half.
Challenging
A scientist is comparing the salinity of two water samples. Sample 1 has 12 grams of salt dissolved in 400 milliliters of water. Sample 2 has 15 grams of salt in 500 milliliters of water. The scientist also has a control solution with a known salt-to-water ratio of 1:30. Which sample is more saline (has a higher salt-to-water ratio) than the control solution?
A.Sample 1 only
B.Sample 2 only
C.Both Sample 1 and Sample 2
D.Neither sample is more saline than the control.
Challenging
Two online streaming services are being compared. Service A has 4 original shows for every 15 licensed shows. Service B's library is known to have a 20% original show rate (meaning 20 out of 100 shows are original). Which service has a higher proportion of original shows?
A.Service A
B.Service B
C.The proportions are the same.
D.It depends on the total number of shows.

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