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LessonsCatch the Flaw

Lesson 20 · Science · Planning a fair test

Step 1 of 4

Find the wrong step

Two children launching different paper planes from different heights
Your lessonPlanning a fair testCore

The Paper-Plane Championship

Jo throws Plane A from the floor. Sam throws Plane B from a chair. Plane B travels farther once.

Plane A
Jo at floor height
Plane B
Sam at chair height

Your question

Can the team conclude that Plane B's design is better?

Lumi’s answer: “Yes. It flew farther, so the design must be better.”

1

Step 1 of 4

Find the wrong step

Find where the reasoning first breaks

Start with Step 1 and move downward. Choose the first line that stops making sense.

Later lines may be wrong too. Pick the first mistake.

Lumi’s work

These lines form one solution. Read them from top to bottom.

  1. 1

    Plane B travelled farther in this trial.

  2. 2

    The plane design was the only difference between the trials.

  3. 3

    That makes the comparison fair.

  4. 4

    So Plane B's design must be better.