There are three main organisers of English language mathematics competitions for which questions sets are easily available on line, namely the UKMT (UK Mathematical Trust), the AMC (American Mathematics Competition) and UOW (The University of Waterloo, Canada).

Below are links to external websites that hold questions sets and answers for these competitions:

1. UKMT Senior Challenge (25 MCQs in 90 minutes);
2. AMC 12 (25 MCQs in 75 minutes);
3. UOW Euclid (10 questions in 2.5 hours).