17M.1.SL.TZ1.T_7

pestleMathematicsAASLPaper 117M· sl-4-6-combined-mutually-exclusive-conditional-independence-prob-diagramssource ↗

Sara regularly flies from Geneva to London. She takes either a direct flight or a non-directflight that goes via Amsterdam.

If she takes a direct flight, the probability that her baggage does not arrive in London is 0.01.
If she takes a non-direct flight the probability that her baggage arrives in London is 0.95.

The probability that she takes a non-direct flight is 0.2.

M17/5/MATSD/SP1/ENG/TZ1/07

Complete the tree diagram.

[3]

Find the probability that Sara’s baggage arrives in London.

[3]

Markscheme / solution

* This question is from an exam for a previous syllabus, and may contain minor differences in marking or structure.

M17/5/MATSD/SP1/ENG/TZ1/07.a/M (A1)(A1)(A1) (C3)

Note: Award (A1) for each correct pair of probabilities.

[3 marks]

$0.8 \times 0.99 + 0.2 \times 0.95$ (A1)(ft)(M1)

Note: Award (A1)(ft) for two correct products of probabilities taken from their diagram, (M1) for the addition of their products.

$= 0.982{\text{ }}\left( {98.2\% ,{\text{ }}\frac{{491}}{{500}}} \right)$ (A1)(ft) (C3)

Note: Follow through from part (a).

[3 marks]

Examiners’ report

[N/A]