Grade 11 Maths · Probability · Paper 1

Probability Notation Grade 11

Real Probability Notation past paper questions and answers from 2023 to 2025, with each memo split into the ticks examiners give. Try one, mark yourself, and see exactly which skill cost you marks.

past paper questions: 9 past paper questions
skills: 2 skills
videos: 2 videos

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Question 10.1 · May/June 2025 · Paper 1 · National (DBE) · 2 marks

10.1 A and B are mutually exclusive events. If

P (A) = 0, 42

and

P (A or B) = 0, 79

, calculate

P (B)

.(2)

Work it out on paper first. Then mark yourself with the official memo, one tick at a time.

Probability Notation skills

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More Probability Notation Grade 11 questions and answers

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4. Question 9.1.1 · November 2024 · Paper 1 · Provincial · 3 marks
9.1 A certain company uses a camera detector system to detect trespassers. Two independent cameras, A and B are installed, one at the front main gate and the other one at the back of the building. If someone trespasses, the probability that the person will be detected by camera A is 0,5 and the probability that the person will be detected by camera B is 0,6.

Answer the questions that follow.
9.1.1 If there is a trespasser, what is the probability that the trespasser will be detected by at least one camera?(3)
Show the memo (3 ticks)Memo
1. ✓
  $0, 5 \times 0, 6$ At least detected by one camera $\Rightarrow$ A or B
  P(A and B) $= 0, 5 \times 0, 6$
  1 mark · Use the product rule for independence
2. ✓
  Substitution into the correct formulaP(A or B) $=$ P(A) $+$ P(B) $-$ P(A and B)
  $= 0, 5 + 0, 6 - (0, 5 \times 0, 6)$
  1 mark · Use the addition rule
3. ✓
  Answer $= 0, 8$
  1 mark · Use the addition rule
5. Question 9.1.1 · November 2023 · Paper 1 · Provincial · 3 marks
9.1 For any two events A and B, it is given that $P (A) = 0, 35$ and $P (A or B) = 0, 61$ . Determine $P (B)$ if:
9.1.1 A and B are mutually exclusive.(3)
Show the memo (3 ticks)Memo
1. ✓
  FormulaFor mutually exclusive events:
  $P (A or B) = P (A) + P (B)$
  1 mark · Use the addition rule
2. ✓
  Substitution $0, 61 = 0, 35 + P (B)$
  1 mark · Use the addition rule
3. ✓
  Answer $P (B) = 0, 61 - 0, 35$
  $= 0, 26$
  1 mark · Use the addition rule

Probability Notation Grade 11 videos

Short lessons from South African teachers first. Videos load only when you tap play, to save your data.

Gr 11 Probability: Complimentary, mutually inclusiveKevinmathscience

Gr 11 Probability: Probability A or BKevinmathscience

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