ACCUPLACER QAS common mistakes
ACCUPLACER QAS · Understand the traps and how to avoid them.
Solving a linear equation by moving a term across the equals sign but forgetting to change its sign, then checking only the final value instead of substituting it back.
Under time pressure the operation is done mentally in one step, and the sign flip is the step most easily dropped because it leaves no visible trace on the page.
What to do instead
Write the subtracted or added term on both sides as a separate line before simplifying, and finish every equation by substituting the answer into the original equation (not the modified one).
Applying a percent increase and then a percent decrease of the same rate and concluding the result equals the original amount.
Percent is treated as an additive quantity rather than a multiplier, so successive changes feel like they should cancel.
What to do instead
Convert each change to a multiplier (increase of 20% is x1.20, decrease of 20% is x0.80) and multiply them; verify with a concrete starting value such as 100.
Mixing up slope and intercept when writing the equation of a line, or reversing the sign of the slope when reading it off two points.
The formula (y2 minus y1) over (x2 minus x1) is recalled as a shape rather than a subtraction order, so numerator and denominator get swapped or subtracted in inconsistent orders.
What to do instead
Always label the two points as (x1,y1) and (x2,y2) before substituting, write the subtraction in the same order top and bottom, and sanity-check by asking whether the line rises or falls left to right.
Reporting the mean of a data set when the question asks which measure is most affected by an outlier, or choosing median without checking whether the data are skewed.
Mean and median are learned as two averages to compute, and the conceptual link between skew or outliers and the choice of measure is under-practised.
What to do instead
Before computing, sketch the data in order and look at the tails; memorise the rule that the mean is pulled toward the tail and the median resists it, then state the reason in terms of the distribution.
Adding the probabilities of two events that can occur together without subtracting the overlap.
The word 'or' is read as simple addition, and the condition of mutual exclusivity is not checked because the problem does not always use that phrase.
What to do instead
Default to P(A or B) = P(A) + P(B) minus P(A and B); explicitly ask whether both events can happen at once, and only drop the subtraction term when they cannot.
Treating dependent selections as independent, for example computing the chance of two red marbles as the product of two identical fractions.
The same multiplication rule is over-applied, and the change in the denominator after a removal is not tracked.
What to do instead
Decide independence first by asking whether the first outcome changes the pool; if it does, adjust both numerator and denominator for the second draw and multiply the two updated fractions.
Reading a value from a table or graph and answering with the raw count when the question asks for a proportion or a conditional share.
The arithmetic feels finished once the number is located, so the final requested form is not re-read.
What to do instead
Underline the exact quantity requested (count, percent, ratio, or 'of those who...') before calculating, and label the numerator and denominator in words before dividing.
Substituting a value into a function or expression and dropping the parentheses, producing a sign error on a negative input.
The substitution is written as adjacent symbols, so a squared negative becomes a negative square.
What to do instead
Replace the variable with the value inside brackets every time, then evaluate the brackets first; for example write f(-3) as the expression with (-3) in place of x before simplifying.
Setting up a ratio or unit-rate problem with the quantities inverted, such as placing hours over miles when the answer requires miles per hour.
The setup is copied from the order the numbers appear in the sentence rather than from the units of the requested answer.
What to do instead
Write the desired unit as a fraction first (miles over hours), then fill each position with the matching number and check that unwanted units cancel.
Rounding intermediate results and then rounding again at the end, so the final answer misses the required precision.
Calculators display rounded values and those get carried forward into later steps.
What to do instead
Keep full precision in intermediate steps, store values in calculator memory if available, and round only once at the final step to the precision the question specifies.