Edexcel Paper 3 2024 June — Question 6 11 marks

Exam BoardEdexcel
ModulePaper 3 (Paper 3)
Year2024
SessionJune
Marks11
PaperDownload PDF ↗
Mark schemeDownload PDF ↗
TopicProbability Definitions
TypeMutually exclusive events
DifficultyStandard +0.3 This is a multi-part Venn diagram probability question requiring understanding of mutually exclusive events, independence, and conditional probability. While it has several parts, each individual step uses standard A-level techniques (identifying mutually exclusive events, applying independence formula P(B∩C)=P(B)P(C), conditional probability formula). The question is slightly easier than average because it's structured with clear scaffolding and uses routine probability definitions rather than requiring novel problem-solving insight.
Spec2.03a Mutually exclusive and independent events2.03b Probability diagrams: tree, Venn, sample space2.03c Conditional probability: using diagrams/tables

  1. The Venn diagram, where \(p , q\) and \(r\) are probabilities, shows the events \(A , B , C\) and \(D\) and associated probabilities.
\begin{figure}[h]
\includegraphics[alt={},max width=\textwidth]{ab7f7951-e6fe-4853-bb69-8016cf3e796c-18_527_1074_358_494} \captionsetup{labelformat=empty} \caption{\(r\)}
\end{figure}
  1. State any pair of mutually exclusive events from \(A\), \(B\), \(C\) and \(D\) The events \(B\) and \(C\) are independent.
  2. Find the value of \(p\)
  3. Find the greatest possible value of \(\mathrm { P } \left( A \mid B ^ { \prime } \right)\) Given that \(\mathrm { P } \left( B \mid A ^ { \prime } \right) = 0.5\)
  4. find the value of \(q\) and the value of \(r\)
  5. Find \(\mathrm { P } \left( [ A \cup B ] ^ { \prime } \cap C \right)\)
  6. Use set notation to write an expression for the event with probability \(p\)

Question 6:
Part (a)
AnswerMarks Guidance
AnswerMark Guidance
\(A, C\) or \(A, D\) or \(B, D\) [Allow things like \(A \cap D\)]B1 For a correct pair; if more than one pair given then all must be correct; \(P(A)\) and \(P(C)\) etc is B0; \(P(A \cap C) = 0\) is B0 but condone \(A \cap C = \varnothing\)
Part (b)
AnswerMarks Guidance
AnswerMark Guidance
\(P(C) = 0.6\) and \(P(B) = p + 0.32\) and \(P(B \cap C) = 0.27\); or \((0.08 + 0.25 + 0.27) \times (0.27 + 0.05 + p) = 0.27\) or \(0.27 + 0.05 + p = \dfrac{0.27}{0.6} = 0.45\)M1 For all relevant labelled probabilities listed or a correct equation/expression for \(p\)
\([p + 0.32 = 0.45\) so\(]\ p = \mathbf{0.13}\)A1
Part (c)
AnswerMarks Guidance
AnswerMark Guidance
\(\left[P(A \mid B')\right] = \dfrac{q}{q+r+0.25+0.08}\) or \(\dfrac{q}{1-(0.05+\text{"0.13"}+0.27)}\) or \(\dfrac{q}{0.55}\)M1 For a correct method for \(P(A \mid B')\) in \(q\) (and \(r\)); ft their \(p\); may be done in stages
\(q + r = 1 - 0.65 - \text{"0.13"}\ [= 0.22]\)M1 For a correct equation for \(q + r\) (o.e.)(ft their \(p\)); can accept \(r = 0\) and \(q = 0.22\)
Since \(r \ldots 0\) the greatest value of \(q\) is "0.22" so \(P(A \mid B')\ ,,\ \mathbf{0.4}\) or \(\dfrac{2}{5}\)A1 For 0.4 i.e. deducing the maximum value of \(P(A \mid B')\); allow ",," 0.4 or \(P(A \mid B') = 0.4\)
Part (d)
AnswerMarks Guidance
AnswerMark Guidance
\(\left[P(B \mid A')\right] = \dfrac{0.27 + \text{"0.13"}}{0.6 + \text{"0.13"} + r} = 0.5\) or \(\dfrac{0.27 + \text{"0.13"}}{1-(q+0.05)} = 0.5\)M1 For a correct equation for \(r\) (or \(q\)) only; can have \(p\) or ft their value for \(p\); may be in stages
\(r = \mathbf{0.07}\)A1
\(q = \mathbf{0.15}\)A1ft
Part (e)
AnswerMarks Guidance
AnswerMark Guidance
\(\left[P\left([A \cup B]' \cap C\right)\right] = [0.25 + 0.08] = \mathbf{0.33}\)B1 For 0.33
Part (f)
AnswerMarks Guidance
AnswerMark Guidance
e.g. \(B \cap [A \cup C]'\) or \(B \cap A' \cap C'\) or \((B \cap A') \cap (B \cap C')\) o.e.B1 For any correct expression; do not condone \(P(\ldots\)
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# Question 6:

## Part (a)
| Answer | Mark | Guidance |
|--------|------|----------|
| $A, C$ or $A, D$ or $B, D$ [Allow things like $A \cap D$] | B1 | For a correct pair; if more than one pair given then all must be correct; $P(A)$ and $P(C)$ etc is B0; $P(A \cap C) = 0$ is B0 but condone $A \cap C = \varnothing$ |

## Part (b)
| Answer | Mark | Guidance |
|--------|------|----------|
| $P(C) = 0.6$ and $P(B) = p + 0.32$ and $P(B \cap C) = 0.27$; or $(0.08 + 0.25 + 0.27) \times (0.27 + 0.05 + p) = 0.27$ or $0.27 + 0.05 + p = \dfrac{0.27}{0.6} = 0.45$ | M1 | For all relevant labelled probabilities listed or a correct equation/expression for $p$ |
| $[p + 0.32 = 0.45$ so$]\ p = \mathbf{0.13}$ | A1 | |

## Part (c)
| Answer | Mark | Guidance |
|--------|------|----------|
| $\left[P(A \mid B')\right] = \dfrac{q}{q+r+0.25+0.08}$ or $\dfrac{q}{1-(0.05+\text{"0.13"}+0.27)}$ or $\dfrac{q}{0.55}$ | M1 | For a correct method for $P(A \mid B')$ in $q$ (and $r$); ft their $p$; may be done in stages |
| $q + r = 1 - 0.65 - \text{"0.13"}\ [= 0.22]$ | M1 | For a correct equation for $q + r$ (o.e.)(ft their $p$); can accept $r = 0$ and $q = 0.22$ |
| Since $r \ldots 0$ the greatest value of $q$ is "0.22" so $P(A \mid B')\ ,,\ \mathbf{0.4}$ or $\dfrac{2}{5}$ | A1 | For 0.4 i.e. deducing the maximum value of $P(A \mid B')$; allow ",," 0.4 or $P(A \mid B') = 0.4$ |

## Part (d)
| Answer | Mark | Guidance |
|--------|------|----------|
| $\left[P(B \mid A')\right] = \dfrac{0.27 + \text{"0.13"}}{0.6 + \text{"0.13"} + r} = 0.5$ or $\dfrac{0.27 + \text{"0.13"}}{1-(q+0.05)} = 0.5$ | M1 | For a correct equation for $r$ (or $q$) only; can have $p$ or ft their value for $p$; may be in stages |
| $r = \mathbf{0.07}$ | A1 | |
| $q = \mathbf{0.15}$ | A1ft | |

## Part (e)
| Answer | Mark | Guidance |
|--------|------|----------|
| $\left[P\left([A \cup B]' \cap C\right)\right] = [0.25 + 0.08] = \mathbf{0.33}$ | B1 | For 0.33 |

## Part (f)
| Answer | Mark | Guidance |
|--------|------|----------|
| e.g. $B \cap [A \cup C]'$ or $B \cap A' \cap C'$ or $(B \cap A') \cap (B \cap C')$ o.e. | B1 | For any correct expression; do **not** condone $P(\ldots$ |

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If you have additional pages with actual mark scheme content, please share those and I'll be happy to extract and format the information as requested.
\begin{enumerate}
  \item The Venn diagram, where $p , q$ and $r$ are probabilities, shows the events $A , B , C$ and $D$ and associated probabilities.
\end{enumerate}

\begin{figure}[h]
\begin{center}
  \includegraphics[alt={},max width=\textwidth]{ab7f7951-e6fe-4853-bb69-8016cf3e796c-18_527_1074_358_494}
\captionsetup{labelformat=empty}
\caption{$r$}
\end{center}
\end{figure}

(a) State any pair of mutually exclusive events from $A$, $B$, $C$ and $D$

The events $B$ and $C$ are independent.\\
(b) Find the value of $p$\\
(c) Find the greatest possible value of $\mathrm { P } \left( A \mid B ^ { \prime } \right)$

Given that $\mathrm { P } \left( B \mid A ^ { \prime } \right) = 0.5$\\
(d) find the value of $q$ and the value of $r$\\
(e) Find $\mathrm { P } \left( [ A \cup B ] ^ { \prime } \cap C \right)$\\
(f) Use set notation to write an expression for the event with probability $p$

\hfill \mbox{\textit{Edexcel Paper 3 2024 Q6 [11]}}