GMAT · Two-Part Analysis · TOPIC LESSON
Solve both column targets, then verify the selected pair against the same model.
BY THE END, YOU CAN
BEFORE YOU START
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01 / UNDERSTAND & APPLY
Two-Part Analysis presents two targets with a shared answer pool. Select one option for each column, following the prompt’s rules about reuse. The two selections may be independent quantities or a linked pair that must satisfy simultaneous constraints.
Label the columns with their meanings, units and ordering restrictions. A correct unordered pair is not enough when the columns have distinct roles. In all exercises here, make exactly two selections, one per named column; reuse is allowed unless the question explicitly rules it out.
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ORIGINAL WORKED EXAMPLE
Select x for Column X and y for Column Y from the common pool {1,2,3,4,5,6}. Given x+y=7, xy=12 and x<y, make exactly one selection per column.
Answer Column X: 3; Column Y: 4
03 / UNDERSTAND & APPLY
When the targets are coupled, solve the relationship before choosing options. Addition or subtraction can eliminate a variable. Then substitute the pair back into every original condition, including inequalities and integer restrictions.
Trying options can also be efficient when the pool is small. Use the strongest condition to form candidate pairs, then test the other condition. Avoid an unrestricted search over all pairs if a simple sum or difference narrows it first.
ORIGINAL WORKED EXAMPLE
Two machines run at constant rates r and s units/hour, with s>r. Together they produce 10 units/hour; the faster produces 2 more units/hour than the slower. Select r and s from {2,3,4,5,6,8}.
Answer r: 4; s: 6
ORIGINAL PRACTICE · 1
x: 6; y: 3
Adding gives 2x=12, so x=6 and y=3. Their sum is 9 and difference 3.
ORIGINAL PRACTICE · 2
a: 3; b: 5
The roots of t²−8t+15=(t−3)(t−5) are 3 and 5. The inequality assigns the smaller to a.
04 / UNDERSTAND & APPLY
Expressions inherit units. If p is dollars per unit, q is a positive count of units and F is dollars, pq and F can be added because both are dollars. F/q+p is dollars per unit. Adding F+p mixes incompatible units.
Dimensional analysis can eliminate an option but may not prove it correct: two different expressions can have the same units. Confirm the actual relationship after the unit check.
ORIGINAL WORKED EXAMPLE
For q>0 units, the bill is a fixed fee F dollars plus p dollars per unit. Select Total cost and Average cost per unit from {F+pq, F/q+p, F+p, q/F+p, Fq+p}; one selection per column.
Answer Total: F+pq; Average: F/q+p
ORIGINAL PRACTICE · 1
Travel time: d/v; Distance in twice that time: 2d
Time is distance/speed in hours. At unchanged speed, twice the time produces twice the distance, 2d kilometers.
05 / UNDERSTAND & APPLY
A multiplicative growth factor acts on the current value. If a quantity rises 25%, multiply by 1.25; do not add 25 unless the unit and statement justify it. Repeating a rate compounds because the second base is the first ending value.
Two-Part targets may ask for the first and second ending values, or for a rate and a starting amount. Label the requested quantities before choosing among tempting related numbers in the pool.
ORIGINAL WORKED EXAMPLE
A fictional account value starts at 80 units and increases by 25% in each of two periods. Select After period 1 and After period 2 from {20,25,80,100,125}; reuse allowed.
Answer After period 1: 100; After period 2: 125
ORIGINAL PRACTICE · 1
Discounted: $180; Final: $198
200×0.90=180; 180×1.10=198. Equal percentage decrease and increase use different bases and do not cancel.
ORIGINAL PRACTICE · 2
After 2: 200; After 3: 400
50×2²=200 and 50×2³=400. Multiplying by the period count would incorrectly give linear growth.
06 / UNDERSTAND & APPLY
A candidate can solve one equation while failing another. Check the complete pair, not each number against a separate fragment of the stem. Reversed roles are another common failure when both values appear in the pool.
For rate problems, ask whether rates add: independent machines working simultaneously on separable output may add; consecutive journey speeds do not generally average arithmetically. The model must match the scenario.
ORIGINAL PRACTICE · 1
Time: 3 hours; A contribution: 12 units
Combined rate=10 units/hour, so time=30/10=3 hours. A makes 4×3=12 units. B makes 18, verifying total 30.
07 / UNDERSTAND & APPLY
A mathematical solution must be permitted by the problem and represented correctly in the answer pool. Counts cannot be fractional when defined as whole items. A rate denominator cannot be zero. Approximate options require sensible rounding rather than an arbitrary nearest-looking number.
If algebra seems to give two admissible ordered pairs but the task expects a unique pair, reread for an ordering, distinctness or domain condition. Do not silently invent one to force uniqueness.
ORIGINAL PRACTICE · 1
a: 5; b: 6
Adding a+b=11 and b−a=1 gives b=6 and a=5. Both are positive, distinct, ordered and in the pool.
08 / UNDERSTAND & APPLY
Read both column labels → translate constraints → decide independent or linked → solve → assign values to columns → verify the pair. This preserves the structure of the question even when the underlying arithmetic is simple.
Two selected responses complete one Two-Part question. In practice review, diagnose whether an error came from computation, modeling or assigning a correct value to the wrong column. Each calls for a different correction.
KEEP THE BIG IDEAS
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