Quantitative Reasoning (37 questions, 35 minutes)
Word problems plus quantitative comparisons, where every wrong answer is a logical error and calculation is often beside the point.
22 topics · 82 questions
Each topic is a path, not a menu: work down it in order and every question builds on the one above. Click any of them to watch the answer draw itself.
Quantitative Reasoning vs Mathematics Achievement
- How it worksHow does a Quantitative Reasoning wrong answer come from bad logic while a Mathematics Achievement wrong answer comes from bad arithmetic?
- How it worksWalk me through the same idea tested twice, once as a reasoning item and once as an achievement item.
- Worked exampleShow me why comparing 40 percent of 80 with 80 percent of 40 is reasoning while computing 40 percent of 80 is achievement.
- Common mistakeWhy isn't Quantitative Reasoning just an easier warm-up for the Mathematics Achievement section?
- Ties togetherHow do the two math sections get paired against each other on the ISEE score report?
Rule Generation: Items That Need No Calculation
- How it worksHow do you find the rule an item is testing before you touch a single number?
- Worked exampleWalk me through why n times m must be a multiple of a times b whenever a divides n and b divides m.
- Worked exampleFind the value of (x + y)2 given that x2 + y2 = 40 and 2xy = 24, without ever solving for x or y.
- Going furtherWhat changes about your approach when the item hands you the rule inside the question?
Sorting Relevant From Irrelevant Information
- How it worksHow do you decide, before computing anything, which numbers in a word problem actually matter?
- Worked exampleFind the muffin revenue when a bakery sells 120 muffins at 2 dollars, 45 scones at 3 dollars, and opens at 6 a.m.
- Common mistakeWhy isn't every number printed in an ISEE word problem needed to answer it?
- Going furtherWhat happens to a problem's difficulty the moment you cross out the numbers you do not need?
The Quantitative Comparison Format
- How it worksHow do the four fixed answer choices work when Column A is set against Column B?
- How it worksWalk me through reading the centered information that sits above the two columns before you compare them.
- Worked exampleCompare the measure of one interior angle of a regular quadrilateral with one interior angle of a regular hexagon.
- Common mistakeWhy isn't the fourth choice, cannot be determined, just there for the questions you find hard?
Comparing Without Computing
- How it worksHow do you strip the same factor off both columns until the comparison becomes obvious?
- Worked exampleCompare 37 times 48 with 38 times 47 without multiplying either product out.
- Worked exampleCompare 3/7 with 5/11 by cross multiplying instead of converting both to decimals.
- Going furtherWhat happens to a cancel-from-both-sides move when the shared factor turns out to be negative?
Testing Strategic Values: 0, 1, a Negative, a Fraction, a Big Number
- How it worksHow does dropping 0, 1, a negative, a fraction and a large number into both columns settle a comparison?
- Worked exampleCompare x squared with x cubed by testing x = 2, then x = 1/2, then x = 0, then x = -2.
- Worked exampleCompare 1/x with x by testing x = 1/2 and then x = 3 and watching the winner flip.
- Common mistakeWhy doesn't one value where Column A wins prove that Column A is always the greater one?
When Cannot Be Determined Is the Answer
- How it worksHow do two test values that tip the balance opposite ways prove a relationship is undetermined?
- Worked exampleCompare 2x with x + 2 when nothing at all is said about x, and show why neither column always wins.
- Going furtherWhat happens to that same comparison the instant the item adds that x is greater than 2?
When Cannot Be Determined Is a Trap
- How it worksHow do you tell a genuinely unknown quantity from one that only looks unknown?
- Worked exampleCompare the square root of 50 with 7, and show why the answer cannot possibly be undetermined.
- Common mistakeWhy isn't I cannot work this out the same thing as the relationship cannot be determined?
- Going furtherWhat happens when a comparison holds a variable but every allowed value gives the same verdict?
Restricted Domains Stated in the Item
- How it worksHow does a stated restriction shrink the set of test values you are allowed to try?
- Worked exampleCompare n squared with n when n is a positive integer, then again when n is any real number.
- Worked exampleCompare 1/(x - 3) with 0 given only that x is greater than 3.
- Common mistakeWhy doesn't the phrase x is a number let you assume x is a whole number?
The Commonest Comparison Error: Computing Everything
- How it worksHow do you spot in two seconds that a comparison is structural rather than arithmetic?
- Worked exampleCompare 25 percent of 880 with 88 percent of 250 without finishing either calculation.
- Common mistakeWhy isn't grinding out both columns the safe choice when you still have time on the clock?
Variables on Both Sides of the Comparison
- How it worksHow do you subtract a matching term from both columns the way you would from both sides of an equation?
- Worked exampleCompare 3a + 7 with 2a + 7 + a and show that the two columns are equal for every value of a.
- Worked exampleCompare 5y - 4 with 4y - 5 when y is known to be negative.
- Going furtherWhat happens to a both-columns move when you are tempted to divide by the variable itself?
Estimation Instead of Exact Arithmetic
- How it worksHow do you round two numbers so your estimate stays on the side of the truth you need?
- Worked exampleFind roughly what 19.6 percent of 4,050 is by rounding it to 20 percent of 4,000.
- Worked exampleFind which is larger, 612 divided by 29 or the number 21, using estimation only.
- Common mistakeWhy doesn't rounding both numbers up always push an estimate in the same direction?
Recognizing Which Operation a Situation Calls For
- How it worksHow does a word problem's wording tell you whether to divide or to multiply?
- Worked exampleFind how many 0.75 liter bottles a 12 liter tank fills, and show why that is division and not multiplication.
- Common mistakeWhy isn't the word of always a signal to multiply and the word less always a signal to subtract?
- Going furtherWhat changes about the setup when the same situation asks for a rate instead of a total?
Comparing and Contrasting Quantities
- How it worksHow do you line two quantities up so that comparing them is actually fair?
- Worked exampleCompare a 30 percent discount followed by a 20 percent discount against one single 50 percent discount.
- Common mistakeWhy isn't a 20 percent rise followed by a 20 percent fall a return to the original price?
Analyzing and Interpreting Data
- How it worksHow do you read a data table for the single comparison the question is actually asking for?
- Worked exampleFind which class improved most when scores moved 62 to 71, 80 to 86, 45 to 58, and 90 to 94.
- Going furtherWhat happens to that conclusion when the question asks for percent change instead of raw change?
Drawing Conclusions From Graphs
- How it worksHow do you read a trend off a line graph without reading any individual point?
- Worked exampleFind the steepest month when a line graph runs 20, 24, 25, 38, 40 across five months.
- Common mistakeWhy doesn't a line that keeps climbing mean the rate of increase is climbing too?
- Going furtherWhat changes about a comparison when two lines are drawn on two different scales?
Reasoning Out the Probability of an Event
- How it worksHow does counting the ways something can fail hand you the probability that it happens?
- Worked exampleCompare the chance that two marbles drawn are both yellow with the chance at least one is, from 3 blue, 4 red, 6 green and 10 yellow.
- Common mistakeWhy doesn't drawing two marbles without replacing the first give the same odds as replacing it?
Concepts and Applications of Measurement
- How it worksHow does one scale factor act differently on a length, on an area and on a volume?
- Worked exampleShow which change doubles a cone's volume, doubling its height or doubling its radius.
- Worked exampleFind how the surface area of a cube changes when every edge is multiplied by 3.
- Common mistakeWhy isn't a shape with the larger perimeter guaranteed to have the larger area?
Arriving at a Statistical Solution
- How it worksHow do the mean, the median and the range each respond when a whole data set shifts up?
- Worked exampleFind the new range after 4 points are added to every score in a set whose range was 35.
- Worked exampleFind the mean of 12, 15, 15, 18 and 40, then the median, and show where the gap comes from.
- Going furtherWhat happens to the mean when one value is dragged far to the right while the median sits still?
Reasoning With Factors and Multiples
- How it worksHow does the statement a divides n turn into something you can multiply through?
- Worked exampleFind what must be true of nm when 6 divides n and 10 divides m, a multiple of 60 or a factor of 60.
- Common mistakeWhy isn't every common multiple of 4 and 6 also a multiple of 24?
Pacing 37 Items in 35 Minutes
- How it worksHow do you budget 35 minutes across 37 items when some of them need no calculation at all?
- Worked exampleWalk me through a 35 minute plan spending 40 seconds on each comparison and 70 on each word problem.
- Going furtherWhat changes about pacing when 5 of the 37 items are unscored and you cannot tell which ones?
No Penalty, So No Blanks
- How it worksHow much does knocking out one of four choices raise what a guess is worth?
- Worked exampleFind the expected number correct from guessing on 8 items after eliminating one choice on each.
- Common mistakeWhy isn't guessing on the ISEE risky the way it is on a test with a quarter point penalty?
- Going furtherWhat changes about your strategy with 90 seconds left and six items still untouched?
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