Unit 4 · Statistics and Probability

4×$5 · 2×$10 · 2×$20 — Which Statements Are True?

Lesson 5 of 6

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Shamira has 4×$5, 2×$10, and 2×$20 notes — 8 total. Three statements are given. Statement 1 (more likely $5 than $20) and Statement 2 (equally likely $5 or not-$5) are both true because exactly half the notes are $5. Statement 3 (certain to pick >$5) is false — there's a 50% chance of picking a $5 note.

Chapters

0:00Introduction
0:22The Question
1:17Analysing Statement 1 (Comparing Note Frequencies)
1:48Analysing Statement 2 (Complementary Probability)
2:18Analysing Statement 3 & final selection
2:51Strategic exam tip
3:25Correct answer

Question

Shamira has these notes in her purse:

- four $5 notes
- two $10 notes
- two $20 notes

She takes a note from her purse without looking.

Which of these statements is/are correct?

  1. She is more likely to take a $5 note than a $20 note.

  2. She is equally likely to take a $5 note or not to take a $5 note.

  3. It is certain that she takes a note worth more than $5.

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