Binomial distribution — Normal approx binomial upper tail

Question

Let . Using a normal approximation (without continuity correction), approximate . Take .

This practice question was inspired by Question 12(c) in the 2024 NSW HSC Mathematics Extension 1 examination, © NESA. It is an original TestMum variation that practises the same mathematical idea, not an official NESA question.

Set up the solution: identify the random variable and its parameters before using the matching probability formula., .
Finish the calculation, then check that the result meets the question’s conditions..
State the final answer clearly in the form the question requested.Answer: .

Common mistake: changing so many features that the new example no longer tests the same mathematical idea.

Verification: Upper-tail uses .

Any mark labels are a TestMum study aid, not an official NESA marking allocation.