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SAT Reading and Writing Practice
Central Ideas and Details

Identify the main idea of a passage and distinguish it from supporting details.

21 original central ideas and details questions in the SAT Ranker bank, with instant scoring and an Elo-based rank once you sign up. Below are a few free samples with full explanations.

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Sample question 1 · medium

Coral reefs occupy less than one percent of the ocean floor, yet they support roughly a quarter of all known marine species. This disproportionate richness stems from the reef's physical structure: the branching, cave-riddled architecture built by coral polyps creates countless microhabitats, each suited to different organisms, in a way that open water simply cannot replicate.

Which choice best states the main idea of the passage?

Coral reefs are shrinking due to ocean temperature changes.
Coral polyps are the primary builders of reef structures.
✓ Reefs support outsized biodiversity because their structure creates varied microhabitats.
Open water contains fewer species than coastal areas.

The passage's core claim is that the physical structure of reefs — not their size — explains their disproportionate biodiversity.

Sample question 2 · hard

Passage 1: Proponents of remote work argue that eliminating commutes gives employees more time for rest and family, boosting long-term productivity and reducing burnout. Passage 2: Critics counter that in-person collaboration accelerates the kind of spontaneous problem-solving that structured video calls rarely replicate, and that many employees report feeling more isolated when working remotely full-time.

Based on both passages, a researcher studying workplace productivity would most likely conclude that

remote work is universally more productive than in-person work.
✓ the productivity effects of remote work involve trade-offs between reduced burnout and reduced spontaneous collaboration.
in-person work has no benefits that remote work cannot replicate.
employee isolation is unrelated to how much time is spent working remotely.

Passage 1 highlights a benefit of remote work (reduced burnout) while Passage 2 highlights a drawback (reduced collaboration, isolation). Together they support a trade-off conclusion, not a one-sided one.

Sample question 3 · easy

Bees are not the only pollinators essential to global food production; bats, moths, beetles, and even some birds contribute significantly to pollinating crops and wild plants alike.

Which choice best states the main idea of the passage?

Bees are the only insects capable of pollination.
✓ Pollination is essential to global food production but relies on more species than just bees.
Bats and birds are more effective pollinators than bees.
Wild plants do not require pollination to reproduce.

The passage's point is that pollination depends on a variety of species beyond bees, not that bees are irrelevant or that other species are superior, matching the second choice.

Sample question 4 · hard

Contrary to the popular image of the lone inventor working in isolation, historical patent records show that most significant technological breakthroughs of the 19th century emerged from clusters of competing inventors working on the same problem within a few years of one another, often independently arriving at similar solutions.

Which choice best states the main idea of the passage?

Patent records from the 19th century are more reliable than records from other periods.
✓ Major 19th-century inventions typically arose from multiple inventors working on similar problems around the same time, not from isolated individuals.
Inventors in the 19th century frequently stole ideas from one another.
Technological progress in the 19th century was slower than in later centuries.

The passage's main point directly challenges the 'lone inventor' image, arguing breakthroughs came from clusters of independently-working inventors, matching the second choice.

Sample question 5 · medium

Cities are often several degrees warmer than surrounding rural areas, a phenomenon driven largely by the prevalence of heat-absorbing surfaces like asphalt and concrete, combined with the reduced tree cover that would otherwise provide shade and release cooling moisture through transpiration.

Which choice best states the main idea of the passage?

Rural areas do not experience any temperature variation.
✓ Urban heat differences result mainly from surface materials and reduced vegetation.
Concrete is a better building material than asphalt.
Trees are the only factor that affects urban temperatures.

The passage attributes city warmth mainly to heat-absorbing surfaces and lower tree cover, matching the second choice. It doesn't claim rural areas have zero variation or that trees are the only factor.

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SAT Reading and Writing skills
Words in ContextCommand of EvidenceInferencesText Structure and PurposeCross-Text ConnectionsRhetorical SynthesisTransitionsBoundariesForm, Structure, and Sense