Chapter 24
This chapter provides you with answers and explanations for the Mathematical Reasoning practice test in Chapter 23. The answers tell you whether you answered the questions right or wrong, but the explanations are even more important. They explain why your answers were right or wrong and give you some hints about the areas tested. Reading the explanations and checking the areas where your answers weren’t the best will help you identify where you should spend more time preparing for the test.
$1,710.00. This problem tests your knowledge and mastery of number operations and number sense. Use a calculator, because numerous conversions are involved, including the following:
Because you have to buy carpet at a full square yard at a time, you’d have to buy 38 square yards.
One square yard of decking costs $45.00, and
or 38 square yards of decking (rounded to the nearest square yard) costs $1,710.00.
average. Quan’s measurements are equal to or higher than those of his class, except for his average. His average is 94 while the class’s average is 94.27. This problem tests your skills in calculations of statistical measurement. You’re asked to use the presented data to calculate the measures of Quan’s performance and compare them to those of his classmates. This is a good question on which to use the calculator because it involves a series of calculations.
You find the average by adding the marks and dividing by the total number of marks. The median is the middle value; in Quan’s case, the middle value is the fourth value 97. Quan’s average was 94, his median was 97, and the range of his marks was 13. The mode is the most often, or common, value in the list, and the range is the difference between the largest and smallest numbers. This question is a good example of why some familiarity with mathematical vocabulary is an asset.
D. 19:18. A number of operations are involved in solving this problem. You’re asked to average a set of grades for each person and compare them by using a ratio. You can simplify this question, using a calculator.
Because you divide each total by 5 to get the average marks for Paula and Dominic, you can simply use the ratio of the totals to get the answer because it will equal the ratio of the averages. (Note that if one of the students had six grades and the other had five, for example, you’d have to use the ratio of the averages, not of the totals.)
The ratio of Paula’s marks to Dominic’s marks is 380:360, which you can simplify by dividing each number by 20 to get 19:18.
66. This problem involves algebra, functions, and patterns. The numbers 4, 6, 10, and 18 form a pattern (also called a series). After looking carefully at the series, you see that the second term is formed by subtracting 1 from the first term and multiplying by 2. Try this on the third number: . You’ve found your pattern. Continuing the series: 4, 6, 10, 18, 34, 66, … , the first term you come to that is a multiple of 11 is 66.
You could also simply double the difference between the previous two numbers and add it to the second number to create the next one. For example, the difference between 4 and 6 is 2. Double that and add it to the to get the next number. The difference between 6 and 10 is 4. Double that and add it to the to get the next number. Continue with this pattern until you find the number you need.
B. $16.13. This problem involves data analysis and manipulation of numbers and is best done using a calculator. Most of the information given is irrelevant, except to decide that Simone may have bought at a high point. The important price to consider is $15.19. In addition to this price per share, Simone has to pay her broker 3% commission.
Therefore, her final price per share on September 24 is . Because you’re dealing with money, you have to round the number to two decimal places, making her final price per share $15.65. This amount of money came out of her bank account for each share she bought.
If Simone decides to sell the shares at this price, $15.65, she has to pay her broker another 3% commission, or . Rounded to two decimals, she has to pay a commission of $0.47 per share. She then receives the value of the shares, $15.65, minus the commission of $0.47, for a total of $15.18 per share — that is, for each share she sells, the broker deposits $15.18 into her account. Notice that this amount is less than the amount she paid for each share.
To break even, Simone has to receive $15.65 per share — after the commission. Set the equation up this way:
Now divide both sides by 0.97 to get .
Cross-multiply and write this equation as . Then, getting rid of the parentheses, the equation looks like this: . Next, bring all the a’s to the left and the numbers to the right, so you have . Then, combine the a’s to get . Finally, divide both sides by 56 to get one a on the left: .
2/3. This question tests your skills in measurement and geometry. You’re asked to find the slope of a line drawn for you.
The x-axis runs horizontally across the grid. The y-axis runs vertically, up and down the grid. The origin is where the two axes (that’s the plural of axis) intersect. Points to the left of the y-axis have negative x-values. Points below the x-axis have negative y-values. The x-intercept of a line is the point where the line cuts the x-axis. The y-intercept of a line is the point where the line cuts the y-axis. All lines parallel to the x-axis have slopes of 0.
The slope of a line is the rise over the run. The rise is 4, and the run is 6. This means that the slope is 4/6 or 2/3 (divide by 2 to simplify).
. This question tests your skills in measurement and geometry. You’re asked to identify the x-intercept and the y-intercept and to draw a line with a slope of 2/3 on the graph.
If you draw a line through the point on the y-axis having the same slope, it crosses the x-axis at . Simply count over 3 points to the left (the run), down 2 (the rise), and you’re at . But you’re asked for the x-intercept, so repeat this process. Go over 3 more points to the left and down 2 more, and you’re at .
A. 3rd quarter. In this question, you’re asked to analyze graphs to identify patterns in a workplace situation.
In the 2013 graph, the third quarter of 2013 produces a little more than 30% of the output. The best answer for this question is the 3rd quarter.
To help you decide which car LeeAnne should buy, create a chart like the following:
Vehicle Type |
Miles/Gallon |
Total Gas Costs |
SUV |
12.8 |
$24,609.38 |
Sedan |
19.6 |
$16,071.43 |
2-door |
19.5 |
$16,153.83 |
All-wheel drive |
17.2 |
$18,313.94 |
Sports car |
18.6 |
$16,935.47 |
From these figures, you can see that the sedan is the best buy. It gets the most miles per gallon, so LeeAnne wouldn’t have to fill the tank as frequently.
D. 11. This question involves data analysis. You’re asked to apply measures of central tendency (the mean) and analyze the effect of changes in data on this measure. If Leonora’s present average is 77.8% and she wants to get an average of 80%, she needs enough marks to get an additional 2.2% .
Because Leonora is taking five subjects, she requires 5 extra points for each percent increase. Thus, she requires additional points. The problem says that English is her best subject, so she would need the 11 extra points in English.
B. the larger rug. This problem tests your measurement skills. You’re asked to predict the impact of changes in the linear dimensions of the rug on its area and cost. Choice (C) seems logical, but the question never mentions the cost of the paneling or the skylight, so you can’t consider it as an answer.
Draw a sketch of the room with the larger rug. It will have a tiled area around it. You have to figure out how many square feet of tile and carpet you need for this floor treatment, as follows:
Item |
Store A |
Store B |
Store C |
Store D |
Average Price |
Friendly Furniture |
Couch |
$1,729.00 |
$1,749.00 |
$1,729.00 |
$1,699.00 |
$1,726.50 |
$1,719.00 |
Dining room set |
$4,999.00 |
$4,899.00 |
$5,019.00 |
$4,829.00 |
$4,936.50 |
$4,899.00 |
Loveseat |
$1,259.00 |
$1,199.00 |
$1,279.00 |
$1,149.00 |
$1,221.50 |
$1,229.00 |
Coffee table |
$459.00 |
$449.00 |
$479.00 |
$429.00 |
$454.00 |
$449.00 |
Reclining chair |
$759.00 |
$799.00 |
$739.00 |
$699.00 |
$749.00 |
$739.00 |
You can see that the only item Friendly Furniture sells for over the average price is the loveseat, which is the answer to the question.
The largest budget is the Operations budget, while the smallest budget is Human Resources. The ratio between these two budgets is 14.7 to 2.1 or 7:1 (dividing both sides by 2.1).
If you wanted to do this in your head, notice that 14:2 (the approximate ratio between the Operations budget and the Human Resources budget) is double 7:1.
D. circle. This question tests your skills in measurement and geometry. To remain at a constant temperature, you have to remain at a constant distance from the fire.
The path of a point that travels a constant distance from a point is a circle.
D. 2,949. This question tests your ability to make a decision based on data presented in a table and then to use that information to answer a question. The least economical car costs $1,823 to drive for a year, while the most economical car costs $840 for the same time under the same conditions. The difference in cost for one year is . The cost for three years is .
You could also estimate an answer. The difference annually is just under $1,000. For three years, that’s just under $3,000. So Choice (D) is the best answer.
(0, 5). This question tests your ability to analyze data by representing data graphically.
For Vehicle A, the difference between the city and highway mileage is 5 miles per gallon . The point you want on the y-axis is (0, 5), which you need to mark on the graph.
A linear equation is one in which the powers of the variables are all equal to 1. To solve this system, you have to eliminate x by multiplying each equation by a number that allows you to subtract one from the other and end up with just y’s. Multiply the first equation by 5 and the second equation by 2:
Subtract the second equation from the first, and you get . (Note that you can also multiply the first equation by and add the two equations together. Either way gets you the same answer.)
The formula for volume of a cylinder (the cylinder is the circular inside of the pool to a height of 9 inches) is , where approximately 3.14, radius, and height. If the diameter is 12 feet, the radius is 6 feet. If the height is 9 inches, it’s 9/12 feet, which can be simplified to 3/4 feet.
In a formula, don’t forget that all units must be the same — that is, feet and feet or inches and inches.
To do this problem in your head, multiply 6 by 6 to get 36. Multiply 36 by 3/4 to get 27, and multiply 27 by 3 to get 81. The approximate volume of the pool is 81 cubic feet, which isn’t bad for an approximation. For your purposes, say the volume is 80 cubic feet, which is still close. The weight of a cubic foot of water is 62.42 pounds, so round it to 60 pounds. Now, multiply 80 by 60 to get 4,800, which is closest to Choice (D). You can go with that approximation because it’s very close to one of the answers.
A. 6.4%. This question tests your ability to evaluate an answer by using a formula. This formula, , isn’t in the format you want because you want to calculate the rate, which means solving for r. You can change the equation to , which allows you to calculate the rate from the information given. Substituting into this equation, you get .
(Remember that 1 year and 3 months is , or 1.25 of a year.)
Then .
C. $4.90. This question involves number operations. You’re asked to calculate — in your head — the answer to a problem.
To use mental math to solve this problem, round everything. Consider the apples at $0.80 a pound, bananas at $0.20 each, milk at $1.30, and a loaf of bread at $1.00. The total for this approximation is . Looking at the answer choices, Choice (C) is the only one close to this approximation.
C. . This question tests your skills in geometry by asking you to visualize a graph of an object. Because the object is a rectangle, the opposite sides are equal in length and are parallel, the fourth corner will be 2 units to the left of the y-axis, giving it an x-coordinate of , and 2 units below the x-axis, giving it a y-coordinate of . Therefore, the point would be .
The x-coordinate is the distance from the y-axis, and the y-coordinate is the distance from the x-axis.