← Senior Mathematics Studio

LEARN · EXPLAIN · REVISE

Independent trials succeed with probability 1/2. Find the least n for success at least once with probability ≥1−2^(−m).

Read the idea, work independently, then explain what changed.

TOPIC 01

Random variables and distributions: mixed review

A mixed assessment: identify the method, justify it and revise your reasoning.

What you will be able to explain

  • Connect the chapter skills without relying on the order of the exercises.

Try it. Leave your reasoning visible.

Use one hint at a time. A correction explains what changed, not just the final answer.

01 / Transfer#Your turn

Independent trials succeed with probability 1/2. Find the least n for success at least once with probability ≥1−2^(−m).

m=3m=3
  • Binomial trials have fixed n, common p and independence; hypergeometric sampling uses a finite population without replacement.
Skills and prerequisite lessons

Working and explanation

BUILD THE REASONING

Hint 1
Express the event with a conditional probability or a disjoint partition.
Hint 2
Use this intermediate relation.
1−2−n≥1−2−m1-2^{-n}\ge1-2^{-m}
Worked solution
  1. Express the event with a conditional probability or a disjoint partition.

  2. Apply the stated relation and retain its conditions.

    2−n≤2−3⇒n≥32^{-n}\le2^{-3}\Rightarrow n\ge3
  3. Use the complementary event of no successes.

The requested value is 3.

Checks and common pitfalls: Use the complementary event of no successes.

Think first. Reveal a hint when the class is ready.

Focus on one question

Teacher preparation and assessment

Question sequence

  • Ask students to name the relevant condition before calculating.

Board plan

  • Compare valid methods and annotate their conditions.

Anticipated thinking

  • A correct final value may still hide a missing assumption.

Assessment checklist

  • Check the method, conditions, reasoning and interpretation separately.

No sign-in. Work stays in this browser. Export before clearing browser data. Written reasoning is assessed with a checklist.

Curriculum and source notes ↗