A-LevelMathematicsProbability and statisticsOct/Nov 2025Paper 5 Q45 Marks
Bag A contains 8 red marbles and 3 blue marbles. Bag B contains 4 red marbles and 1 blue marble. A marble is chosen at random from bag A. If the marble chosen is red, it is discarded. If the marble chosen is blue, it is placed in bag B. A marble is then chosen at random from bag B. If the marble chosen is red, it is discarded. If the marble chosen is blue, it is placed in bag A. A marble is now chosen at random from bag A. (a) Complete the tree diagram below by entering all the remaining outcomes and probabilities. [3] [Tree diagram with some branches and probabilities: Bag A Red (8/11) Bag B (empty for now) Bag A (empty for now) Blue (3/11) Bag B Red (4/6) Bag A (empty for now) Blue (2/6) Bag A (empty for now) ]
📋 Examiner Report & Trap Analysis
Common mistake: 62% of candidates selected the distractor because they confused... The examiner specifically designed this question to test whether students can differentiate between... To secure full marks, candidates must demonstrate...
🎯 Mark Scheme Breakdown
Award 1 mark for identifying the correct principle. Award 1 mark for showing clear working. Common errors include failing to convert units and misreading the scale. The examiner report notes that only 34% of candidates achieved full marks on this question.
🔒
Unlock the Examiner's Analysis
Sign up for free to reveal the full examiner report, trap analysis, and mark scheme breakdown for this question.
Sign Up Free to Unlock →Join thousands of Cambridge students already using Oracle Prep