SEAMO 2027 - Paper E - SET 05 - Self-study Question 1

Question 1

SEAMO self-study edition 2027; not an official 2027 paper. Original source years are retained. 25 questions, 90 minutes; Q1–10: 3 points, Q11–20: 4 points, Q21–25: 6 points, total 100. Original response types and all subparts are preserved. Verified is an editorial convention; source defects, necessary assumptions and unresolved mathematical uncertainty are disclosed.

In a pack of 10 watches, 3 are known to be defective. If 2 watches are selected at random from the pack, what is the probability that at least one is defective?

$\frac2{11}$
$\frac1{13}$
$\frac3{13}$
$\frac7{15}$
$\frac8{15}$