PrepTest 136 · Section 2 · Question 10

Owen's Kite Ceiling

Owen built a kite for the spring fair. "If I make the frame lighter, and keep it just as strong, it will fly higher," he explained to Kevin. Kevin nodded while drawing a pterodactyl. "But I can't shave the sticks any thinner without making them flimsy. So my kite can't fly any higher. That's that." Priya walked over with her juice box. "Hold on. You found one way to fly higher, and that way is blocked. But are there other ways? A longer tail? A bigger sail? A windier hill?" Owen blinked. "Hmm. I just figured lighter was the only trick." "That's the plank your whole argument stands on," Priya said. "If there's any other trick, your 'can't' turns into 'maybe.'" Kevin held up his drawing. "Pterodactyls just flap harder."

A lighter kite frame that is just as strong would let the kite fly higher. But the frame can't be made lighter without becoming weaker. So the kite can't be made to fly higher.

The argument relies on which assumption?

The Case of the Slow Sled

"Your Honor," said attorney Gloria Finch, "my client's sled cannot go any faster. Waxing the runners would speed it up, but the only wax allowed would crack them. So, no faster sled. Case closed." Mr. Whitfield rose, adjusting his suspenders. "Ms. Finch has shown one door is locked. She has not shown it is the only door." He counted on his fingers. "A steeper hill. A lighter rider. A smoother run." Judge Okafor leaned in. "So her argument assumes waxing is the only way to go faster?" "Precisely, Your Honor. Take that plank away and the 'cannot' becomes a 'might.'" Ms. Finch sat down very slowly.