Logical Reasoning Questions: 20 Worked Examples by Question Type

Q1

The Verrick Library is moving its entire microfilm archive out of the upstairs reading room and into a climate-controlled basement store. The archive holds about twelve thousand reels, most of them local newspapers printed in the last century. The head archivist argues that the move will extend the life of the collection, because humidity in the reading room swings widely across the year, and such swings are the main cause of microfilm degradation. Nothing else about the way the film is handled or stored will change. The argument depends on assuming which one of the following?

1. AMicrofilm is the most valuable material the library holds.
2. BNone of the microfilm in the collection has already been damaged by humidity.
3. CHumidity in the basement store will not swing as widely as it does in the reading room.
4. DThe library spends more on the basement store than it does on the reading room.
5. EReaders will consult the microfilm less often once it has been moved.

Q7

Nutrition writer: In a study of four hundred households, the amount of food thrown away fell by an average of 18 percent in the year after the household installed a chest freezer. The households kept weekly diaries of everything they discarded, and each had bought its freezer at its own expense. Buying a chest freezer is therefore an effective way for a household to cut its food waste. The writer's argument depends on assuming which one of the following?

1. AChest freezers use less electricity than upright freezers.
2. BEvery household in the study threw away less food after installing the freezer.
3. CFood waste is the largest single component of household rubbish.
4. DHouseholds that already own a freezer throw away no food at all.
5. EThe fall in waste was not produced by some other change the households made at the same time as installing the freezer.

Q13

Agronomist: In our trials, plots planted with the new cover crop lost 12 percent less soil moisture to evaporation over the dry season than bare plots did. The trials ran on twelve paired plots across two dry seasons, with soil moisture logged weekly at three depths. Since moisture is what limits yields in this region, farmers who plant the cover crop between harvests can expect higher yields. The agronomist's argument depends on assuming which one of the following?

1. AThe cover crop does not take up, in its own growth, more soil moisture than it saves from evaporating.
2. BEvaporation is the only way this region's soils lose moisture.
3. CLeaving soil bare between harvests is the usual practice in the region.
4. DThe cover crop can be sown with equipment farmers in the region already own.
5. ENo other region would benefit from planting the cover crop.

Q19

Conservation officer: Otter numbers in the Wynn have recovered steadily since the pesticide that was washing into it was banned across the valley. In neighbouring rivers, where the pesticide is still used, otter numbers have not recovered. Numbers have been surveyed on the Wynn each spring since the ban, and on three neighbouring rivers since 2019. We should extend the ban to the whole catchment so that otters there recover too. The officer's argument depends on assuming which one of the following?

1. AThe pesticide brings farmers no benefit that other methods could not provide.
2. BOtters are the only species harmed by the pesticide.
3. COtter numbers in the Wynn have returned to their historic level.
4. DWhat is holding otter numbers down in the neighbouring rivers is something the ban would remove.
5. EFarmers in the catchment would stop using the pesticide even without a ban.

Q2

Since Brantham council replaced its town-centre parking meters with a mobile payment app, revenue from town-centre parking has fallen 22 percent. The figure covers the twelve months since the change and is measured in the same way as in previous years. A council member concludes that the app is driving shoppers away from the town centre and should be scrapped, and has asked officers to price the reinstatement of the meters. Which one of the following, if true, most weakens the council member's conclusion?

1. AThe app charges exactly the hourly rates the old meters charged.
2. BIn the same month the app launched, the council opened a free municipal car park two streets from the main shopping street.
3. CThe council recovered the cost of installing the app within its first year.
4. DSeveral town-centre retailers had asked the council to modernise the way parking is paid for.
5. EThe meters the app replaced had been in service for more than thirty years.

Q8

Pinewood Insurance offers a discount to drivers who fit a telematics device that reports harsh braking. Over three years, drivers with the device filed 30 percent fewer claims than drivers without one. Pinewood's analysts conclude that being monitored makes people drive more safely, and the company now plans to require the device of every policyholder. The device has been offered since 2021, and about one policyholder in six has so far fitted one. Which one of the following, if true, most weakens the analysts' conclusion?

1. ADrivers who chose to fit the device already had cleaner driving records, on average, than drivers who did not.
2. BThe device costs Pinewood about forty pounds per driver per year to run.
3. CThe discount is smaller than the premium increase that follows a claim.
4. DA rival insurer offers a device that reports several behaviours besides braking.
5. EHarsh braking is only one of several behaviours known to predict crash risk.

Q14

Ferrow School began requiring students to hand in their phones at the start of each day; the phones are returned at the end of the day, and the rule applies to every year group. In the following term the number of disciplinary referrals recorded at the school fell by half. The head teacher credits the phone rule and has recommended it to other schools. Which one of the following, if true, most weakens the head teacher's reasoning?

1. AA few students found ways of handing in one phone while keeping another.
2. BSome teachers found collecting and returning the phones time-consuming.
3. CMost parents said they supported the new rule.
4. DIn the same term, the school stopped recording lateness as a referral; lateness had previously accounted for about half of all referrals.
5. EReferrals at Ferrow had been rising for three years before the rule was introduced.

Q20

Gym owner: Our 6 a.m. classes are the least attended on the timetable. Two instructors currently cover them, and the rooms used for evening classes are not yet at capacity, so extra evening classes could be added without any other change. If we cancel the early classes and move those two instructors to the busy evening slots, total class attendance will rise. Which one of the following, if true, most weakens the owner's reasoning?

1. AThe 6 a.m. classes have been on the timetable for two years.
2. BThe evening classes are taught by the gym's most experienced instructors.
3. CAlmost all of the members who attend the 6 a.m. classes are unable to attend at any other time.
4. DSeveral instructors have said they prefer working early in the morning.
5. EThe gym's membership has grown by 10 percent this year.

Q3

At the Kelso Ridge site, archaeologists recovered a cluster of grinding stones from a pit that also contained charred grain, dated to roughly nine thousand years ago. The pit lay beneath a collapsed shelter and appears not to have been disturbed since it was filled. They conclude that the people living there processed wild grain into flour, rather than simply gathering it and storing it whole. Which one of the following, if true, most strengthens the archaeologists' conclusion?

1. AGrinding stones of similar shape have been found at sites two hundred kilometres away.
2. BThe pit also held fragments of tightly woven storage baskets.
3. CThe grain belongs to a species that still grows wild in the region today.
4. DStarch grains matching the charred grain were found embedded in the working surfaces of the grinding stones.
5. EThe site shows signs of occupation over at least four centuries.

Q9

Transit planner: Evening ridership on the number 12 bus fell sharply after we cut its evening service from every ten minutes to every twenty. The cut was made two years ago to save money; the route's stops, its fares and its daytime frequency were all left unchanged, and evening ridership is counted automatically as passengers board. Restoring the ten-minute evening service would bring ridership back to its former level. Which one of the following, if true, most strengthens the planner's prediction?

1. AThe number 12 route serves the city's largest hospital.
2. BThe city owns enough buses to run the more frequent evening service.
3. CDaytime ridership on the number 12 also fell slightly over the same period.
4. DOn the number 7 route, evening ridership returned to its former level within four months of a ten-minute service being restored after a similar cut.
5. EFuel prices have risen since the evening service was cut.

Q15

Ornithologist: Nest boxes fixed to the north side of trunks in Ashgrove Wood fledged 30 percent more chicks than boxes on the south side. Insect abundance, measured all summer, was the same on both sides of the wood. Sixty boxes were monitored through a single breeding season, thirty on each side. I conclude that it is the cooler midday temperature inside north-facing boxes that raises fledging success. Which one of the following, if true, most strengthens the ornithologist's conclusion?

1. AThe north-facing boxes were on average slightly older than the south-facing ones.
2. BEvery box in the study was fixed at the same height above the ground.
3. CIn an unusually cool summer, when midday temperatures inside south-facing boxes stayed within the range recorded in north-facing ones, the gap in fledging success almost disappeared.
4. DThe wood contains both oak and beech trees.
5. EFledging success across the whole wood was higher this year than last.

Q4

A fitness magazine invited its readers to fill in an online survey about exercise. Of the readers who replied, 78 percent said they exercise at least four times a week. The survey ran for six weeks and drew just over four thousand replies. The magazine's editor, describing that as an unusually large sample, concluded that most people in the country now exercise at least four times a week. The editor's reasoning is most vulnerable to criticism on the grounds that it

1. Atreats people who read a fitness magazine and chose to reply as representative of the country as a whole
2. Bassumes without argument that exercising four times a week is good for people
3. Cmistakes an effect for its cause
4. Ddraws a conclusion about the present from evidence about the past
5. Etreats a percentage as though it were a raw number

Q10

Support manager: After we introduced the new ticketing system, our team's average first-response time improved from nine hours to five. Over the same period our customer satisfaction score did not move at all. The score comes from the same monthly survey we have always used, sent to the same number of customers. Clearly our customers do not care how quickly we respond. The manager's reasoning is flawed because it

1. Aassumes that the new ticketing system was what made responses faster
2. Btreats an average as though it described every individual case
3. Coverlooks the possibility that other things affecting satisfaction got worse over the same period
4. Ddraws a conclusion about all customers from the experience of a single team
5. Econfuses customer satisfaction with customer loyalty

Q16

Editor: We published 140 articles last year, and every one of the 22 that ran over two thousand words drew above-average reader engagement. Our writers currently choose their own length, and the shorter pieces were spread right across the range from four hundred words upwards. To raise engagement this year, we should require every article to run over two thousand words. The editor's reasoning is most vulnerable to criticism on the grounds that it

1. Afails to specify how reader engagement is measured
2. Bassumes that padding an article out to two thousand words would give it whatever made the long articles engaging
3. Ctakes above-average engagement to be desirable without arguing for it
4. Dgeneralises from a single year to every year
5. Econfuses an average with a total

Q5

Every employee at Hallam Freight who holds a Class B licence is also trained in hazardous-materials handling. Nobody who works in the dispatch office holds a Class B licence. All of the company's night-shift drivers hold a Class B licence. The company employs one hundred and eighty people in total across its depot, its dispatch office and its driving rotas, and every licence held by an employee is recorded centrally and reviewed each January. If the statements above are true, which one of the following must also be true?

1. ANobody in the dispatch office is trained in hazardous-materials handling.
2. BEveryone at Hallam Freight who is trained in hazardous-materials handling holds a Class B licence.
3. CEvery night-shift driver at Hallam Freight is trained in hazardous-materials handling.
4. DAll hazardous-materials training at Hallam Freight takes place on the night shift.
5. EAt least one dispatch office employee has applied for a Class B licence.

Q11

All of the pottery recovered from the lower level of the Marden excavation is glazed. None of the glazed pottery found anywhere at Marden bears a maker's mark. Some of the pottery from the upper level bears a maker's mark. The excavation ran for three seasons; every piece recovered was catalogued by level as it came out of the ground, and no piece was assigned to more than one level. If the statements above are true, which one of the following must also be true?

1. ANone of the pottery from the upper level is glazed.
2. BSome of the pottery from the upper level is not glazed.
3. CEvery piece of unglazed pottery at Marden comes from the upper level.
4. DThe pottery from the lower level is older than the pottery from the upper level.
5. EMost of the pottery found at Marden is glazed.

Q17

Municipal rule: a building may be listed as historic only if it is at least eighty years old and retains its original façade. The Corley Mill, completed in 1994, retains its original façade. The Ashby Warehouse was built in 1901 and has had its façade replaced twice. Listing brings a maintenance grant and restricts what an owner may alter, and the council reviews applications twice a year. If the statements above are true, which one of the following must also be true?

1. AAny building at least eighty years old that retains its original façade is listed as historic.
2. BThe Corley Mill will be listed as historic in 2074.
3. CThe Ashby Warehouse would be listed as historic if its original façade were restored.
4. DThe Corley Mill is the older of the two buildings.
5. ENeither the Corley Mill nor the Ashby Warehouse can currently be listed as historic.

Q6

Critic: The new bridge design should be rejected, because it has never been used for a span this long. Engineer: Every bridge design was untested once, including the cantilever design that now carries a million vehicles a day across the harbour. If never having been tried were a reason to reject a design, we would still be building nothing but stone arches. The engineer responds to the critic by

1. Apresenting statistical evidence that the new design is safe
2. Bshowing that the critic's principle, applied consistently, would rule out designs the critic accepts
3. Cquestioning whether the critic is qualified to judge bridge designs
4. Dconceding the critic's objection but arguing that the benefits outweigh it
5. Epointing out that the critic has described the new design inaccurately

Q12

Columnist: Supporters of the harbour redevelopment say it will create two thousand jobs. The same consultancy forecast three thousand jobs for the airport expansion, and only nine hundred appeared. The harbour report runs to ninety pages and uses the same modelling approach the consultancy applied to the airport. Until that gap has been explained, the harbour figure should not be treated as reliable. The columnist's argument proceeds by

1. Ashowing that the harbour forecast rests on a definition of 'job' that is too broad
2. Barguing that the redevelopment would do more harm than good
3. Coffering an alternative and lower estimate of the number of jobs
4. Dclaiming that the supporters stand to profit personally from the project
5. Equestioning a forecast on the strength of its source's record on a comparable forecast

Q18

Economist A: Raising the city's minimum wage will reduce employment among young workers. Economist B: When Ridgeport raised its minimum wage by 12 percent in 2019, youth employment there rose by 3 percent over the following twelve months. Economist A: Ridgeport's economy grew 4 percent that year, its fastest rate in a decade. The question is not whether youth employment rose, but whether it rose by less than it otherwise would have. Economist A responds to B's counterexample by

1. Aarguing that B's evidence does not separate the effect of the wage rise from other influences on employment
2. Bdisputing the accuracy of the Ridgeport employment figures
3. Coffering a counterexample of A's own
4. Dnarrowing the original claim so that it applies to a smaller group of workers
5. Egranting B's point while arguing that it matters less than B supposes