Comparing Rational Numbers
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ISEE Upper Level: Quantitative Reasoning › Comparing Rational Numbers
Three friends are comparing their quiz scores. Anna scored $$\frac{17}{20}$$, Ben scored $$84.5%$$, and Carol scored $$0.847$$. If they want to arrange their scores from lowest to highest, what is the correct order?
Carol, Ben, Anna
Anna, Ben, Carol
Ben, Anna, Carol
Ben, Carol, Anna
Explanation
When comparing numbers in different formats, you need to convert them all to the same format to determine their relative order. This question tests your ability to work flexibly with fractions, percentages, and decimals.
Let's convert all three scores to decimals for easy comparison. Anna scored $$\frac{17}{20}$$, which equals $$17 \div 20 = 0.85$$. Ben scored $$84.5%$$, which converts to $$84.5 \div 100 = 0.845$$. Carol scored $$0.847$$, which is already in decimal form.
Now we can easily compare: Ben has $$0.845$$, Anna has $$0.85$$, and Carol has $$0.847$$. Arranging from lowest to highest: $$0.845 < 0.847 < 0.85$$, so Ben, Carol, Anna. The correct answer is B) Ben, Anna, Carol.
Looking at the wrong answers: Choice A) Anna, Ben, Carol suggests Anna scored lowest, but $$0.85$$ is actually the highest score. Choice C) Carol, Ben, Anna puts Carol lowest, but $$0.847$$ is the middle score, not the lowest. Choice D) Ben, Carol, Anna correctly identifies Ben as lowest but incorrectly places Carol above Anna when $$0.847 < 0.85$$.
Study tip: Always convert mixed formats to the same type before comparing. Decimals are usually easiest since you can compare place values directly. Watch for small differences—here, all three scores were very close (within $$0.005$$ of each other), so careful conversion and comparison were essential.
If $$x = \frac{13}{30}$$ and $$y = 43.\overline{3}%$$, which statement about the relationship between $$x$$ and $$y$$ is true?
$$x < y$$ because $$43.\overline{3}% = \frac{13}{30}$$ when converted to a fraction
$$x < y$$ because $$\frac{13}{30} \approx 0.433$$ while $$43.\overline{3}% \approx 0.434$$
$$x > y$$ because fractions are generally larger than percentages under 50%
$$x = y$$ because both expressions represent the same rational number
Explanation
When comparing fractions and percentages, you need to convert them to the same form to make an accurate comparison. This question tests your ability to work with repeating decimals and recognize equivalent representations of rational numbers.
Let's convert both values to see their relationship. First, convert $$x = \frac{13}{30}$$ to a decimal by dividing: $$13 ÷ 30 = 0.4\overline{3}$$ (where the 3 repeats infinitely). Now convert $$y = 43.\overline{3}%$$ to decimal form by dividing by 100: $$43.\overline{3} ÷ 100 = 0.4\overline{3}$$. Since both equal $$0.4\overline{3}$$, we have $$x = y$$.
You can also verify this by converting the percentage to a fraction. Since $$43.\overline{3} = 43\frac{1}{3} = \frac{130}{3}$$, we get $$43.\overline{3}% = \frac{130/3}{100} = \frac{130}{300} = \frac{13}{30}$$, which equals $$x$$.
Choice A is wrong because the size relationship between numbers doesn't depend on their format—fractions aren't inherently larger than percentages. Choice B incorrectly states that $$x < y$$ even while correctly noting they're equal when converted. Choice D makes a calculation error by approximating $$43.\overline{3}%$$ as 0.434 instead of recognizing that $$43.\overline{3} = 43\frac{1}{3}$$ exactly.
When working with repeating decimals on standardized tests, look for patterns involving fractions with denominators like 3, 6, 9, or 30. Converting $$\overline{3}$$ patterns to fractions with 3 in the denominator often reveals the exact relationship.
In a survey, $$\frac{3}{7}$$ of students preferred math, $$42.9%$$ preferred science, and $$0.428$$ preferred English. Which subject was most preferred?
Science and English are tied, since $$42.9% = 0.429$$ and both exceed $$\frac{3}{7}$$
Math, because $$\frac{3}{7}$$ is the largest value when compared to the others
English, because $$0.428$$ is smaller than the others, indicating a measurement error
Science, because $$42.9%$$ is greater than both $$\frac{3}{7}$$ and $$0.428$$
Explanation
When comparing quantities expressed in different formats—fractions, percentages, and decimals—you need to convert them all to the same format to make accurate comparisons.
Let's convert all three values to decimals to compare them directly. For math: $$\frac{3}{7} = 3 \div 7 = 0.428571...$$ or approximately $$0.429$$. For science: $$42.9% = \frac{42.9}{100} = 0.429$$. English is already given as $$0.428$$.
Now we can compare: Math ≈ $$0.429$$, Science = $$0.429$$, and English = $$0.428$$. Science has the highest value at exactly $$0.429$$, making it the most preferred subject.
Looking at the wrong answers: Choice A incorrectly assumes $$\frac{3}{7}$$ is largest without doing the conversion—this is a common trap when students don't convert to compare properly. Choice C makes no mathematical sense; it suggests that a smaller value indicates a measurement error, which has no basis in the problem. Choice D claims science and English are tied, but this ignores that $$42.9% = 0.429$$ while English preference is $$0.428$$—these are clearly different values.
The correct answer is B because $$42.9%$$ equals $$0.429$$, which is greater than both $$\frac{3}{7}$$ (approximately $$0.429$$ but slightly less) and $$0.428$$.
Study tip: Always convert fractions, decimals, and percentages to the same format before comparing. Decimals are usually the easiest common denominator for these comparisons.
Three stores offer discounts: Store X gives $$\frac{1}{8}$$ off, Store Y gives $$12.6%$$ off, and Store Z gives $$0.124$$ off the regular price. Which store offers the smallest discount?
Store Y, because $$12.6% = 0.126$$ which is greater than the other discounts
Store Z, because $$0.124 < 0.125 < 0.126$$ when all discounts are compared
Store X, because $$\frac{1}{8} = 0.125$$ which is the smallest decimal value
Store X and Z offer equal discounts, both smaller than Store Y's discount
Explanation
When comparing discounts given in different formats, you need to convert everything to the same form—either all decimals, all percentages, or all fractions—to make an accurate comparison.
Let's convert all three discounts to decimals. Store X offers $$\frac{1}{8}$$ off, which equals $$1 ÷ 8 = 0.125$$. Store Y gives $$12.6%$$ off, which converts to $$12.6 ÷ 100 = 0.126$$. Store Z offers $$0.124$$ off, which is already in decimal form.
Now we can compare: $$0.124 < 0.125 < 0.126$$. Store Z offers the smallest discount at $$0.124$$, making choice B correct.
Choice A incorrectly identifies Store X as having the smallest discount. While it correctly calculates that $$\frac{1}{8} = 0.125$$, it fails to properly compare this with the other values. Choice C makes an error in reasoning—it correctly converts $$12.6% = 0.126$$ but then claims this larger value represents a smaller discount, confusing "greater than" with "smallest discount." Choice D incorrectly states that Stores X and Z offer equal discounts, when $$0.125 ≠ 0.124$$.
Strategy tip: Always convert mixed formats to the same unit before comparing. Write out the decimal equivalents to three decimal places when dealing with percentages and fractions to avoid rounding errors. Remember that the smallest decimal represents the smallest discount amount.
A student claims that $$\frac{9}{20}$$ is less than $$44.9%$$ because "fractions are always smaller than percentages." What is wrong with this reasoning?
The comparison is correct but the general rule about fractions and percentages is invalid
Fractions and percentages cannot be compared without converting to a common form
The reasoning is correct; $$\frac{9}{20} = 45%$$ which is greater than $$44.9%$$
The statement about fractions and percentages is false, and $$\frac{9}{20} > 44.9%$$
Explanation
When comparing fractions and percentages, you need to convert them to the same form to make an accurate comparison. The student's claim contains both a mathematical error and a flawed general rule.
Let's convert $$\frac{9}{20}$$ to a percentage: $$\frac{9}{20} = \frac{9 \times 5}{20 \times 5} = \frac{45}{100} = 45%$$. Since $$45% > 44.9%$$, the fraction is actually greater than the percentage, not less than it.
The student's reasoning that "fractions are always smaller than percentages" is completely false. The numerical relationship between a fraction and a percentage depends on their actual values, not their forms. For example, $$\frac{1}{2} = 50%$$ (equal), $$\frac{3}{4} = 75%$$ (fraction represents a larger value than $$60%$$), and $$\frac{1}{10} = 10%$$ (fraction represents a smaller value than $$25%$$).
Looking at the answer choices: Choice A incorrectly states the reasoning is correct when it isn't. Choice B suggests you can't compare fractions and percentages, but you absolutely can after converting to a common form. Choice D agrees the comparison is correct ($$\frac{9}{20} < 44.9%$$), which is mathematically wrong.
Choice C correctly identifies both problems: the general statement about fractions and percentages is false, and $$\frac{9}{20}$$ is actually greater than $$44.9%$$.
Study tip: Always convert fractions and percentages to the same form before comparing. To convert a fraction to a percentage, multiply by 100 or find an equivalent fraction with denominator 100.
In a class election, candidate Alpha received $$\frac{2}{5}$$ of votes, candidate Beta received $$39.8%$$ of votes, and candidate Gamma received $$0.402$$ of votes. Who won the election?
Gamma, because $$0.402 > 0.4 > 0.398$$ when all votes are compared
Alpha and Gamma tied, since $$\frac{2}{5}$$ and $$0.402$$ are approximately equal
Beta, because $$39.8%$$ represents the largest share of votes cast
Alpha, because $$\frac{2}{5} = 0.4$$ which is the highest percentage of votes
Explanation
When comparing fractions, percentages, and decimals, you need to convert everything to the same format to determine which is largest.
Let's convert all votes to decimals for easy comparison:
- Alpha: $$\frac{2}{5} = 0.400$$
- Beta: $$39.8% = 0.398$$
- Gamma: $$0.402$$ (already in decimal form)
Now you can clearly see: $$0.402 > 0.400 > 0.398$$, making Gamma the winner with the highest vote share.
Looking at the wrong answers: Choice A incorrectly claims $$\frac{2}{5} = 0.4$$ is the highest. While the conversion is correct, $$0.4 = 0.400$$, which is less than Gamma's $$0.402$$. Choice C suggests Beta has the largest share, but $$39.8% = 0.398$$ is actually the smallest of the three values. Choice D claims Alpha and Gamma tied because their values are "approximately equal," but $$0.400$$ and $$0.402$$ are not equal—Gamma's lead of $$0.002$$ represents 0.2 percentage points, which could mean several votes in a real election.
The correct answer is B because when you convert all three vote shares to comparable decimal form, Gamma's $$0.402$$ is indeed the largest.
Strategy tip: When comparing mixed formats (fractions, percentages, decimals), always convert to the same format first. Decimals are usually easiest for comparison since you can line up place values directly.
Three athletes' success rates are recorded as $$\frac{14}{25}$$, $$55.9%$$, and $$0.56\overline{1}$$. If they want to determine who has the best performance, what should they conclude?
The athlete with $$\frac{14}{25}$$ has the best performance at exactly $$56%$$
The athlete with $$55.9%$$ has the best performance as it exceeds the others
The athlete with $$0.56\overline{1}$$ has the best performance as it represents the highest rate
All three athletes have essentially identical performance rates within measurement error
Explanation
When comparing rates given in different formats, you need to convert them all to the same form to make accurate comparisons. This question tests your ability to work with fractions, percentages, and repeating decimals.
Let's convert all three rates to decimals for easy comparison. First, $$\frac{14}{25} = \frac{14 \times 4}{25 \times 4} = \frac{56}{100} = 0.56$$. Second, $$55.9% = 0.559$$. Third, $$0.56\overline{1}$$ means the digit 1 repeats infinitely, so this equals $$0.561111... = \frac{505}{900} = \frac{101}{180} \approx 0.5611$$.
Comparing these values: $$0.559 < 0.56 < 0.5611$$. The athlete with $$0.56\overline{1}$$ has the highest success rate, making choice C correct.
Choice A is wrong because $$\frac{14}{25} = 0.56 = 56%$$, not "exactly 56%" as something special, and it's not the highest rate anyway. Choice B is incorrect because $$55.9%$$ is actually the lowest of the three rates, not exceeding the others. Choice D is wrong because these rates are meaningfully different—the gap between the highest and lowest is about 0.002, which represents a clear performance difference, not measurement error.
Study tip: When comparing numbers in mixed formats on the ISEE, always convert to the same form first. Be especially careful with repeating decimals—the overline notation means those digits repeat forever, often making the value larger than it initially appears.
In a survey about transportation preferences, $$\frac{5}{12}$$ chose cars, $$41.\overline{6}%$$ chose public transit, and $$0.41\overline{7}$$ chose walking. Which transportation method was least preferred?
Cars, because $$\frac{5}{12} = 0.41\overline{6}$$ which is the smallest value
Public transit, because $$41.\overline{6}% = 0.41\overline{6}$$ which is the smallest value
Cars and public transit are tied for least preferred, both less than walking
Walking, because $$0.41\overline{7}$$ is the largest value, indicating the question asks for least preferred
Explanation
When comparing different number formats like fractions, percentages, and decimals, you need to convert everything to the same form to make accurate comparisons.
Let's convert all three values to decimals. First, $$\frac{5}{12} = 5 \div 12 = 0.41\overline{6}$$ (where the 6 repeats). Next, $$41.\overline{6}% = 41.666...% = 0.41\overline{6}$$ as a decimal. Finally, walking is already given as $$0.41\overline{7}$$ (where the 7 repeats).
Now we can compare: cars = $$0.41\overline{6}$$, public transit = $$0.41\overline{6}$$, and walking = $$0.41\overline{7}$$. Since $$0.41\overline{7} > 0.41\overline{6}$$, walking received the highest preference, while cars and public transit are tied for the lowest preference.
Choice A incorrectly states that $$\frac{5}{12}$$ is the smallest value, but it's actually tied with public transit, not smaller. Choice B makes the same error, claiming public transit alone is smallest when it's tied with cars. Choice C confuses the question's logic—it correctly identifies that $$0.41\overline{7}$$ is largest but then incorrectly concludes this means it's least preferred, when the largest percentage actually indicates the most preferred option.
Remember to always convert mixed number formats to the same form before comparing, and pay careful attention to repeating decimals—the difference between $$0.41\overline{6}$$ and $$0.41\overline{7}$$ is small but significant for determining order.
A student argues that $$0.\overline{571428} = \frac{4}{7}$$ and therefore $$0.\overline{571428} > 57%$$. Is this argument valid?
No, because even if $$0.\overline{571428} = \frac{4}{7}$$, we have $$57% > \frac{4}{7}$$
Yes, because $$\frac{4}{7} = 0.\overline{571428}$$ and this repeating decimal is greater than $$0.57$$
No, because $$0.\overline{571428} ≠ \frac{4}{7}$$ so the premise is incorrect
Yes, because $$\frac{4}{7} ≈ 0.571$$ and $$57% = 0.57$$, so $$0.571 > 0.57$$
Explanation
This question tests your understanding of repeating decimals, fraction conversions, and decimal comparisons. When you see notation like $$0.\overline{571428}$$, the bar indicates that the digits 571428 repeat infinitely.
Let's verify the student's claim that $$0.\overline{571428} = \frac{4}{7}$$. When you divide 4 by 7 using long division, you get exactly 0.571428571428..., which is indeed $$0.\overline{571428}$$. So the first part of the argument is correct.
Now we need to compare this to 57%. Converting the percentage: $$57% = 0.57 = 0.570000...$$. Since $$0.\overline{571428} = 0.571428571428...$$ and $$57% = 0.570000...$$, we can see that the repeating decimal is larger because 0.571428... > 0.570000.... Therefore, $$\frac{4}{7} > 57%$$, making the student's argument valid.
Choice A is incorrect because it approximates $$\frac{4}{7}$$ as 0.571, but the actual value is $$0.\overline{571428}$$, which continues infinitely. While the conclusion happens to be right, the reasoning uses an approximation rather than the exact value.
Choice C is wrong because $$0.\overline{571428}$$ does equal $$\frac{4}{7}$$ - you can verify this through long division.
Choice D is incorrect because $$\frac{4}{7} = 0.\overline{571428} > 0.57 = 57%$$, not the other way around.
Study tip: When comparing repeating decimals to regular decimals, convert both to the same form and compare digit by digit from left to right.
A meteorologist reports that the probability of rain is $$\frac{7}{20}$$ on Monday, $$35.2%$$ on Tuesday, and $$0.348$$ on Wednesday. On which day is rain most likely?
Tuesday, because $$35.2% = 0.352$$ which is the highest probability
Wednesday, because $$0.348$$ represents the highest probability value
Monday and Wednesday have equal probability, both higher than Tuesday
Monday, because $$\frac{7}{20} = 0.35$$ which is the highest probability
Explanation
When comparing probabilities given in different formats, you need to convert everything to the same format to make accurate comparisons. Probabilities can be expressed as fractions, percentages, or decimals, but they all represent the same underlying concept.
Let's convert all three probabilities to decimals. For Monday: $$\frac{7}{20} = 7 \div 20 = 0.35$$. For Tuesday: $$35.2% = 35.2 \div 100 = 0.352$$. Wednesday is already given as a decimal: $$0.348$$.
Now we can easily compare: Monday = 0.35, Tuesday = 0.352, Wednesday = 0.348. Since 0.352 is the largest value, Tuesday has the highest probability of rain.
Choice A incorrectly states that Monday has the highest probability. While the conversion $$\frac{7}{20} = 0.35$$ is correct, 0.35 is not the highest value among the three days. Choice C makes the error of assuming that 0.348 is the highest probability without properly comparing all three converted values. Choice D incorrectly claims that Monday and Wednesday have equal probabilities—they don't (0.35 ≠ 0.348)—and also incorrectly states these are higher than Tuesday's probability.
The correct answer is B because Tuesday's probability of 0.352 is indeed the highest when all probabilities are expressed in decimal form.
Study tip: Always convert different probability formats to the same form before comparing. Decimals are usually easiest for comparison since you can directly see which decimal is larger without additional calculation.