Target practice with hit probability 0.3 per shot and 10 shots. What is the probability of at least one hit?

Difficulty: Easy

Correct Answer: 1 - (0.7)^10

Explanation:


Introduction / Context:
With independent trials, the probability of “at least one success” is one minus the probability of “no success at all.” Here, success = hit, p = 0.3 per shot, n = 10 shots.



Given Data / Assumptions:

  • Per-shot hit probability p = 0.3, miss probability q = 0.7.
  • Number of shots n = 10 (independent).


Concept / Approach:
P(≥1 hit) = 1 − P(0 hits) = 1 − q^n with q = 0.7.



Step-by-Step Solution:
P(0 hits) = (0.7)^{10}.Therefore P(≥1 hit) = 1 − (0.7)^{10}.



Verification / Alternative check:
As p increases or n grows, the probability approaches 1, consistent with intuition.



Why Other Options Are Wrong:
(0.7)^10 is the probability of zero hits; (0.3)^10 is “all hits” if inverted (actually all-hit probability is (0.3)^{10}); 1 is only true in the limit, not exactly; 1 − (0.3)^10 is not the correct complement.



Common Pitfalls:
Confusing “at least one” with “exactly one,” or complementing the wrong event.



Final Answer:
1 - (0.7)^10

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