ITPEC IP April 2025 Question 4
ITPEC IP April 2025 — Question 4 of 100
125/216 — each throw must produce one of the five faces other than 1.
For one fair six-sided die throw, the probability of not getting 1 is 5/6. The three throws are independent, so multiply the probability for all three: (5/6)³ = 125/216. This counts every three-throw sequence made only from 2 through 6.
Answer (d)
Why not others:
- (a) 1/216 is the probability of one particular three-result sequence, such as three 1s
- (b) 5/72 does not apply the independent-event product correctly
- (c) 91/216 is neither the all-no-1 probability nor its complement; the complement is 1 - 125/216 = 91/216, which is the probability of at least one 1
Key rule: For independent repeated events, multiply their probabilities; use the complement only when it simplifies the desired event.
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