Comparing Rational Numbers
Help Questions
ISEE Middle Level: Quantitative Reasoning › Comparing Rational Numbers
Which of the following numbers is between 4/9 and 52%?
3/7
11/25
9/20
8/15
Explanation
To find a number between 4/9 and 52%, first convert both to decimals. 4/9 ≈ 0.444... and 52% = 0.52. We are looking for a number n such that 0.444... < n < 0.52. Let's evaluate the choices: A) 3/7 ≈ 0.428, which is less than 0.444... B) 11/25 = 0.44, which is less than 0.444... C) 9/20 = 0.45, which is between 0.444... and 0.52. D) 8/15 ≈ 0.533, which is greater than 0.52. Thus, 9/20 is the only value in the specified range.
Compare the quantities in Column A and Column B.
Column A: 87% of 50
Column B: 50% of 87
The two quantities are equal.
The quantity in Column B is greater.
The relationship cannot be determined from the information given.
The quantity in Column A is greater.
Explanation
The phrase 'percent of' implies multiplication. Column A is 0.87 * 50. Column B is 0.50 * 87. Due to the commutative property of multiplication (a * b = b * a), the order of the factors does not change the product. Therefore, 0.87 * 50 = 50 * 0.87. The two quantities are equal. We can calculate both to verify: 0.87 * 50 = 43.5. 0.50 * 87 = 43.5.
On a science test, Alex answered 4/5 of the questions correctly. Ben answered 83% of the questions correctly, and Chandra answered 0.81 of the questions correctly. Who had the highest score?
Alex and Chandra had the same highest score.
Alex
Chandra
Ben
Explanation
To determine who had the highest score, we need to compare the three values by converting them to a common format, such as decimals. Alex's score: 4/5 = 0.80. Ben's score: 83% = 0.83. Chandra's score: 0.81. Comparing the decimals, 0.83 is the largest number. Therefore, Ben had the highest score.
Information for the following question: -1 < x < 0
Compare the quantities in Column A and Column B.
Column A: x
Column B: 1/x
The quantity in Column B is greater.
The quantity in Column A is greater.
The relationship cannot be determined from the information given.
The two quantities are equal.
Explanation
Let's choose a value for x that is between -1 and 0. For example, let x = -1/2. Then Column A is -1/2. Column B is 1/(-1/2) = -2. Comparing -1/2 and -2, we see that -1/2 is greater because it is closer to zero on the number line. For any number x between -1 and 0, its reciprocal 1/x will be a number less than -1. A number between -1 and 0 is always greater than a number less than -1. Therefore, the quantity in Column A is always greater.
Mixture A contains juice and water in a ratio of 2:5. Mixture B has a juice concentration of 30%. Which statement is true?
Mixture B has a higher juice concentration than Mixture A.
Both mixtures have the same juice concentration.
Mixture A has a higher juice concentration than Mixture B.
The relationship cannot be determined from the information given.
Explanation
The concentration of juice in Mixture A is the amount of juice divided by the total amount of the mixture. The ratio is 2 parts juice to 5 parts water, so the total is 2+5=7 parts. The concentration is 2/7. To compare 2/7 with Mixture B's concentration of 30%, convert both to decimals or percentages. 2/7 ≈ 0.2857, which is 28.57%. Mixture B's concentration is 30%. Since 30% > 28.57%, Mixture B has a higher juice concentration.
Which of the following values is greatest?
0.62
5/8
13/20
62.8%
Explanation
To compare the values, convert all of them to decimals. 5/8 = 0.625. 0.62 remains 0.62. 62.8% = 0.628. 13/20 = 0.65. Comparing the decimals, 0.65 is the largest value. Therefore, 13/20 is the greatest.
Arrange the following numbers from least to greatest: -3/5, -0.61, -58%, -0.606
-58%, -3/5, -0.606, -0.61
-0.61, -3/5, -58%, -0.606
-0.61, -0.606, -3/5, -58%
-58%, -0.606, -3/5, -0.61
Explanation
First, convert all numbers to decimals to compare them easily. -3/5 = -0.6. -58% = -0.58. The numbers are -0.6, -0.61, -0.58, and -0.606. For negative numbers, the one with the largest absolute value is the smallest. So, the order from least to greatest is -0.61, -0.606, -0.6, -0.58. This corresponds to the list -0.61, -0.606, -3/5, -58%.
Information for the following question: y is a positive integer.
Compare the quantities in Column A and Column B.
Column A: $(3/4)^y$
Column B: $(4/5)^y$
The quantity in Column B is greater.
The two quantities are equal.
The relationship cannot be determined from the information given.
The quantity in Column A is greater.
Explanation
When comparing exponential expressions with the same positive integer exponent, you need to focus on the bases. Since both expressions have the same exponent $$y$$ (where $$y$$ is a positive integer), the key is determining which base is larger.
Let's compare the bases: $$\frac{3}{4} = 0.75$$ and $$\frac{4}{5} = 0.8$$. Since $$0.8 > 0.75$$, we know that $$\frac{4}{5} > \frac{3}{4}$$.
For any positive integer exponent, if the base is larger, the result will be larger. This means $$\left(\frac{4}{5}\right)^y > \left(\frac{3}{4}\right)^y$$ for any positive integer $$y$$. You can verify this with a simple example: when $$y = 2$$, $$\left(\frac{3}{4}\right)^2 = \frac{9}{16} = 0.5625$$ while $$\left(\frac{4}{5}\right)^2 = \frac{16}{25} = 0.64$$.
Choice A incorrectly suggests Column A is greater, likely from miscomparing the fractions or confusing the relationship between bases and results. Choice B is wrong because we can definitively determine the relationship—we have enough information since both bases are positive and different. Choice C is incorrect because the bases are different, so the exponential expressions cannot be equal for any positive integer exponent.
Therefore, D is correct: Column B is greater.
Study tip: When comparing exponential expressions with the same positive exponent, convert the bases to decimals to quickly see which is larger. The larger base always produces the larger result.
Information for the following question: 0 < a < b < 1
Compare the quantities in Column A and Column B.
Column A: 1/a
Column B: 1/b
The two quantities are equal.
The relationship cannot be determined from the information given.
The quantity in Column B is greater.
The quantity in Column A is greater.
Explanation
When comparing two positive fractions, taking the reciprocal reverses the inequality. Since it is given that a < b, it follows that 1/a > 1/b. We can test this with numbers. Let a = 1/3 and b = 1/2. Both are between 0 and 1, and 1/3 < 1/2. Column A is 1/(1/3) = 3. Column B is 1/(1/2) = 2. Since 3 > 2, the quantity in Column A is greater. This holds for any values of a and b that fit the given conditions.
Compare the quantities in Column A and Column B.
Column A: The price of a $90 item after a 1/5 discount.
Column B: The price of an $85 item after a 15% discount.
The quantity in Column A is greater.
The two quantities are equal.
The relationship cannot be determined from the information given.
The quantity in Column B is greater.
Explanation
Calculate the sale price for each column. Column A: The discount is (1/5) * $90 = $18. The sale price is $90 - $18 = $72. Column B: The discount is 15% of $85, which is 0.15 * $85 = $12.75. The sale price is $85 - $12.75 = $72.25. Comparing the two prices, $72.25 is greater than $72. Therefore, the quantity in Column B is greater.