Strategy, probability generating function.
[STEP III 2014 Question 13 (Probability and Statistics)]
Probability generating function, sum of independent random variables, expectation and variance algebra, coin toss.
[STEP III 2011 Question 12 (Probability and Statistics)]
Probability generating function, dice, six, expectation.
[STEP III 2000 Question 13 (Probability and Statistics)]
Underground Mathematics: Selected worked STEP questions
STEP Question database
University of Cambridge Mathematics Faculty: What do we look for?
University of Cambridge Mathematics Faculty: Information about STEP
University of Cambridge Admissions Office: Undergraduate course information for Mathematics
Stephen Siklos' "Advanced Problems in Mathematics" book (external link)
MEI: Worked solutions to STEP questions (external link)
OCR: Exam board information about STEP (external link)
AMSP (Advanced Maths Support programme): Support for University Admission Tests (external link)