Weekly Challenge
Five original questions for the week of August 24, 2026. No timer. Check each answer as you go.
The new subway line will pay for itself within ten years, because fare revenue is projected to cover construction costs by then.
The argument assumes that
Fare revenue can only cover construction if it is not eaten up by operating costs first. If maintenance swallows the revenue, the line never pays for itself.
All successful marathons require months of training. Jan ran a successful marathon. Therefore, Jan trained for months.
Which of the following exhibits the same pattern of reasoning?
Both are: All X are Y. This is X. Therefore this is Y. The other choices change the structure (most, reversed, some).
You should buy this brand of running shoes. Three Olympic sprinters wear them, and they are the fastest runners in the world.
The reasoning is most vulnerable to criticism because it
This is an appeal to authority by celebrity. The sprinters may wear the shoes for sponsorship money, not because the shoes are better.
The committee approved every proposal submitted before noon. The solar panel proposal was submitted at 11:30 a.m. and was not approved.
Which of the following must be true?
If every pre-noon proposal were approved, the 11:30 proposal would be approved. Since it was not, the "every" claim must have an exception.
Researchers found that cities with more public libraries have higher literacy rates. They conclude that libraries improve literacy.
Which of the following, if true, most strengthens the conclusion?
A before-and-after comparison with a control group is the classic strengthener. It rules out the "wealth explains both" alternative in A.
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Last updated October 12, 2026