Supported by
Supported by
            British Mathematical Olympiad                                       2003/4 British Mathematical Olympiad
          Round 1 : Wednesday, 3 December 2003                                                 Round 1
                                                                      1. Solve the simultaneous equations
Time allowed Three and a half hours.
Instructions • Full written solutions - not just answers - are            ab + c + d = 3,   bc + d + a = 5,      cd + a + b = 2,   da + b + c = 6,
               required, with complete proofs of any assertions          where a, b, c, d are real numbers.
               you may make. Marks awarded will depend on the
               clarity of your mathematical presentation. Work
                                                                      2. ABCD is a rectangle, P is the midpoint of AB, and Q is the point
               in rough first, and then draft your final version         on P D such that CQ is perpendicular to P D.
               carefully before writing up your best attempt.            Prove that the triangle BQC is isosceles.
               Do not hand in rough work.
             • One complete solution will gain far more credit
                                                                      3. Alice and Barbara play a game with a pack of 2n cards, on each of
               than several unfinished attempts.        It is more
                                                                         which is written a positive integer. The pack is shuffled and the cards
               important to complete a small number of questions
                                                                         laid out in a row, with the numbers facing upwards. Alice starts, and
               than to try all five problems.                            the girls take turns to remove one card from either end of the row,
             • Each question carries 10 marks.                           until Barbara picks up the final card. Each girl’s score is the sum of
             • The use of rulers and compasses is allowed, but           the numbers on her chosen cards at the end of the game.
               calculators and protractors are forbidden.                Prove that Alice can always obtain a score at least as great as
                                                                         Barbara’s.
             • Start each question on a fresh sheet of paper. Write
               on one side of the paper only. On each sheet of
               working write the number of the question in the        4. A set of positive integers is defined to be wicked if it contains no
               top left hand corner and your name, initials and          three consecutive integers. We count the empty set, which contains
               school in the top right hand corner.                      no elements at all, as a wicked set.
                                                                         Find the number of wicked subsets of the set
             • Complete the cover sheet provided and attach it to
               the front of your script, followed by the questions                              {1, 2, 3, 4, 5, 6, 7, 8, 9, 10}.
               1,2,3,4,5 in order.
             • Staple all the pages neatly together in the top left
               hand corner.                                           5. Let p, q and r be prime numbers. It is given that p divides qr − 1,
                                                                         q divides rp − 1, and r divides pq − 1.
                            Do not turn over until told to do so.        Determine all possible values of pqr.