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LessonsCatch the Flaw

Lesson 03 · Maths · Multi-step percentages

Step 1 of 4

Find the wrong step

Lumi comparing two robot rescue routes with different battery costs
Your lessonMulti-step percentagesStretch

The Robot Rescue

Rita and Max guide rescue robots along different routes. The pilot with more battery remaining at the final door must unlock it.

Rita starts
78% battery
Rita's route
3 stages × 12 percentage points
Max starts
64% battery
Max's route
2 stages × 9.5 percentage points

Your question

Whose controller has more battery at the final door?

Lumi’s answer: “Rita's does, because she started 14 percentage points ahead.”

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

    Rita uses 3 × 12% = 36%. She finishes with 78% − 36% = 42%.

    Multiply the repeated drain before subtracting it from the starting charge.

  2. 2

    Max uses 2 × 9.5% = 19%. He finishes with 64% − 19% = 45%.

  3. 3

    Compare their starting charges: 78% > 64%.

  4. 4

    Conclusion: Rita should unlock the final door.