AMO 2021 – Primary 6 (Grade 6) Question 7

Question 7

Four classroom lights work independently. Each has a $90\%$ probability of still working after $1000$ hours. What is the probability that at least one is still working then?

Question illustration

$90.50\%$
$99.99\%$
$98.88\%$
$95.00\%$
$89.10\%$