Question Types — GRE General Questions

7 GRE General practice questions on Question Types, part of Quantitative Reasoning. Below are 7 of them in full, each with the answer and a written explanation.

Questions & explanations

1. When dealing with percent change, always pick a convenient number like 100 to avoid fractions.

For percent increase/decrease problems, set the original value to 100. Then compute the final value and find the difference. This avoids dealing with variables and reduces calculation errors.

2. For ratio problems, use the 'multiply ratios' trick: to combine ratios, multiply the fractions.

If a:b = 3:4 and b:c = 2:5, then a:c = (3/4)*(2/5)=6/20=3/10. This works because the b terms cancel. Always ensure the common term is in the denominator of one and numerator of the other.

3. For geometry problems with perimeter and area, set up a system of equations and solve by substitution.

Given perimeter and area of a rectangle, write l+w = P/2 and lw = A. Substitute w = P/2 - l into lw = A to get a quadratic. Solve for l and w, then identify the longer side.

4. In probability without replacement, multiply conditional probabilities step by step.

For drawing two marbles without replacement, P(both red) = P(first red) * P(second red | first red). Always adjust the total count and favorable count after each draw.

5. Plug in Numbers: Choose strategic values like 0, 1, -1, fractions, and large numbers to test relationships. If different values yield different comparisons, answer is D.

For QC with variables, plugging in numbers is key. Always test boundary values and typical cases. If one value gives A>B and another gives B>A, then answer is D.

6. Avoid Trap: When variables are not constrained, the answer is often D. But if constraints are given (e.g., x>0), the relationship may be fixed. Always check the domain.

For example, compare x^2 and x. If x>1, x^2 > x; if 0<x<1, x^2 < x. Without constraint, answer is D. With constraint x>1, answer is A.

7. Simplify Both Columns: Perform the same operation on both sides (add, subtract, multiply, divide) to simplify. Be cautious with multiplication/division by negative numbers (reverses inequality) or zero.

For example, compare (x+1)^2 and x^2+2x+1. Expand both: they are equal. So answer is C. Always simplify algebraically first.

More Quantitative Reasoning topics

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