Diez preguntas del banco del curso
Las diez preguntas siguientes están tomadas, sin cambios, del banco de práctica de Seeking English: 1,000 preguntas del GMAT Focus Edition con explicación, el porqué de cada opción incorrecta y la trampa típica de cada pregunta. El banco completo está incluido en la cuota del curso GMAT. Elegimos cuatro de Problem Solving, tres de Critical Reasoning, dos de Data Sufficiency y una de Two-Part Analysis, todas de nivel básico o medio.
Quantitative Reasoning
1. A ferry travels at a constant speed of 42 miles per hour. How many miles does it travel in 2.5 hours?
Explanation. Distance equals rate times time, so the ferry covers 42×2.5 = 105 miles in 2.5 hours.
Trap: multiplying the rate by the wrong number of hours.
2. If 3x + 2y = 27 and x + 2y = 13, what is the value of x?
Explanation. Subtracting the second equation from the first eliminates y: (3x + 2y) − (x + 2y) = 27 − 13, so 2x = 14 and x = 7.
Trap: subtracting the equations in the wrong order, using only one equation, or stopping before the final division.
3. In a survey of 80 city residents, 50 said they use public transit, 35 said they bike, and 15 said they use both. How many of the residents surveyed use neither public transit nor biking?
Explanation. The number of residents who use at least one of the two services is 50 + 35 − 15 = 70, by the two-set overlap formula. Subtracting this from the total of 80 gives the number who use neither: 80 − 70 = 10.
Trap: stopping at the union count instead of subtracting it from the total.
4. A paper mill's daily output was reduced to 15 of what it had been. After the reduction, the mill produces 40 rolls per day. By what percent did the daily output decrease?
Explanation. The old output is 40÷15 = 40×5 = 200 rolls, a drop of 200 − 40 = 160 rolls. Percent change divides by the starting value: 160200 = 0.80, an 80 percent decrease.
Trap: dividing the change by the ending value instead of the starting value.
Verbal Reasoning
5. Corvid Motors introduced a mandatory pre-shift equipment check for its assembly line workers. In the following quarter, the number of workplace injuries fell by twenty-five percent. Plant management concludes that the equipment check caused the drop in injuries.Which of the following, if true, most helps to justify the plant management's reasoning?
Explanation. The argument is causal, crediting the equipment check for lower injuries. Ruling out every other safety, staffing, or equipment change during the quarter removes rival explanations and leaves the check as the one change that could have produced the drop.
Trap: ruling out concurrent causes.
6. Thornfield Community College began offering a mandatory freshman orientation seminar three years ago. Since then, the proportion of freshmen who return for a second year has risen from seventy percent to eighty-two percent. College administrators argue that the orientation seminar is responsible for the improvement in retention and are considering expanding it to two full weeks.Which of the following, if true, most seriously weakens the administrators' argument?
Explanation. The administrators credit the seminar for a retention gain that began at the same time the seminar did. If larger financial aid packages also began three years ago, reduced financial hardship could be driving students to stay enrolled, and the seminar would deserve none of the credit currently assigned to it.
Trap: a second simultaneous change mistaken for a coincidence.
7. At Renner School District, the average score on the mathematics exam fell compared with the previous administration of the exam. At the same time, the percentage of students who scored high enough to pass the exam rose.Which of the following, if true, most helps to explain this finding?
Explanation. An average can fall even while most students do better, if a small group scores far below everyone else and drags the mean down without pulling many students below the passing threshold. New students unfamiliar with the material, scoring especially poorly, fit that description: they lower the average sharply while leaving the pass rate, which depends only on how many cross the threshold, unaffected or even improved. A uniformly harder exam would instead be expected to lower both figures together, which is why that choice deepens the puzzle instead of resolving it.
Trap: a fact that would move both figures the same way, instead of one that explains why they moved apart.
Data Insights
8. A garden contains only tulip bulbs and daffodil bulbs, planted in the ratio 2 to 3. How many tulip bulbs are in the garden?(1) The garden contains 30 daffodil bulbs.
(2) The garden contains 50 bulbs in total.
Explanation. The ratio of tulip bulbs to daffodil bulbs is fixed at 2 to 3, so tulip bulbs make up 25 of all the bulbs. Statement (1) alone: 30 daffodil bulbs correspond to 3 parts of the ratio, so one part is 10 bulbs and tulip bulbs number 2×10 = 20. Sufficient. Statement (2) alone, with statement (1) covered: 50 bulbs in total split into 2 + 3 = 5 parts of 10 bulbs each, so tulip bulbs again number 2×10 = 20. Sufficient. Each statement alone pins the tulip count at 20 — consistent with each other, since 50 bulbs split 2 to 3 gives exactly 20 tulip and 30 daffodil bulbs — so the answer is D.
Trap: the hidden D, from missing that a fixed ratio plus any one absolute quantity determines the whole split.
9. The price of an appliance was increased by 20 percent and then decreased by p percent. Was the appliance's final price greater than its original price?(1) p = 15
(2) p is less than 20.
Explanation. Starting from an original price of 1, the two changes multiply the price by 1.2×(1 − p100), which exceeds 1 exactly when p is less than 1006≈16.67. Statement (1) alone: with p = 15, the multiplier is 1.2×0.85 = 1.02, greater than 1 — a definite yes. Sufficient. Statement (2) alone, with statement (1) covered: p less than 20 permits p = 5, giving a multiplier of 1.2×0.95 = 1.14 and a yes, and it also permits p = 18, giving a multiplier of 1.2×0.82 = 0.984 and a no. Not sufficient. Since statement (1) alone gives an invariable answer and statement (2) alone does not, the answer is A.
Trap: assuming any percent decrease smaller than the percent increase must leave the price higher.
Section A of a course has 20 students with an average exam score of 72. Section B has 30 students with an average exam score of 82.
Select the combined average exam score of all 50 students, and select the combined total of all exam points scored by the 50 students. Make only one selection in each column.
| Combined average exam score of all 50 students | Combined total of all exam points scored by the 50 students | |
|---|---|---|
| 72 | ||
| 77 | ||
| 78 | ||
| 82 | ||
| 3850 | ||
| 3900 |
Explanation. Section A's total points are 20×72 = 1440 and Section B's are 30×82 = 2460, for a combined total of 1440 + 2460 = 3900 points across 20 + 30 = 50 students. The combined average is 3900÷50 = 78.
Trap: averaging two group averages without weighting by group size.
Scored entirely in your browser. Nothing is sent to any server and there is no form to fill in. These ten items are the easy and medium tiers of the bank; the full bank runs to level 5.
Si te interesa el banco completo (990 preguntas más, incluidos los niveles 4 y 5, Reading Comprehension, Table Analysis, Graphics Interpretation y Multi-Source Reasoning), viene incluido con el curso GMAT de Seeking English, junto con las clases en vivo y la revisión de simulacros. También puedes hacer el test corto de seis preguntas, que cubre las tres secciones.
Un ejemplo de cada formato
Doce preguntas escritas por nosotros al estilo del examen, una por cada formato que vas a encontrar, incluidos los que el bloque anterior no cubre: Reading Comprehension, Table Analysis, Graphics Interpretation y Multi-Source Reasoning. La respuesta está oculta hasta que la abras; intenta cada una con cronómetro antes de mirarla.
Quantitative Reasoning
Problem Solving · arithmeticA store marks a coat down by 20 percent and then takes a further 25 percent off the already reduced price. What percent of the original price does the customer pay?
- 45%
- 55%
- 60%
- 65%
- 75%
Problem Solving · number propertiesIf n is a positive integer and n2 is divisible by 24, what is the largest integer that must divide n?
- 2
- 4
- 6
- 12
- 24
Problem Solving · work ratesMachine A fills a tank in 6 hours and machine B fills it in 3 hours. They start together, and A is switched off after 1 hour. How long does it take in total to fill the tank?
- 2 h
- 2 h 15 min
- 2 h 30 min
- 2 h 45 min
- 3 h
Rates add; times do not. Always work in "fraction of the job per hour".
Problem Solving · statisticsThe average (arithmetic mean) of five numbers is 20. If the largest number is removed, the average of the remaining four is 15. What was the number removed?
- 25
- 30
- 35
- 40
- 45
Verbal Reasoning
Critical Reasoning · weakenA city council argues that widening Main Street will reduce traffic congestion downtown, because the two other streets that were widened last year now carry more cars per hour than before. Which of the following, if true, most weakens the argument?
- Main Street is longer than either of the two streets widened last year.
- The two widened streets now attract drivers who previously used other routes, and total downtown travel time has not fallen.
- The widening project on Main Street would take fourteen months to complete.
- Some residents of Main Street oppose the project.
- Public transit ridership downtown fell slightly last year.
In weaken questions, find the unstated premise (here: "more flow = less congestion") and the option that denies it.
Critical Reasoning · assumptionCompany X's sales rose 30 percent in the quarter after it began advertising on streaming platforms. Therefore, streaming advertising is an effective way for Company X to raise sales. The argument depends on which assumption?
- Company X's competitors do not advertise on streaming platforms.
- The 30 percent increase was not primarily caused by factors other than the streaming campaign.
- Streaming advertising is cheaper than television advertising.
- Company X's sales had never risen 30 percent in a single quarter before.
- Streaming platforms reach a younger audience than television.
Reading Comprehension · inferencePassage (excerpt): "Although early economists treated consumer preferences as fixed, later research showed that the order in which options are presented measurably alters which option is chosen. This finding does not imply that preferences are random; rather, it suggests that stated preferences are constructed at the moment of choice from cues in the environment." — The passage suggests that the author would most likely agree with which statement?
- Consumer choices cannot be predicted.
- Early economists were correct that preferences are stable.
- The context in which a choice is made influences the preference that is expressed.
- Later research has been rejected by most economists.
- Randomness is the main determinant of consumer behavior.
In inference questions the correct answer is almost always the most modest one: the one you can prove from the text without adding anything.