IB Maths AA SL 4.11 Formal conditional probability Question Bank

Practise IB Mathematics SL/HL 4.11 by applying formal conditional probability methods to exam-style questions.

Exam points

identify the mathematical structure, variable or representation
select and apply the correct theorem, formula or algorithm
check the result using units, domain, graph or logical reasoning

[Maximum number: 2]

The following cumulative frequency graph shows the monthly income, I dollars, of 2000 families.

Figure for Question SL 4.11—Formal conditional probability question 1 — IB Maths AA SL

A family is chosen at random.

Find the probability that this family lives in an apartment, given that its monthly income is greater than 4000 dollars.

correct working/probability for number of families
eg $\quad 122+28, \frac{150}{2000}, 0.075$
0.186666
$\frac{28}{150}\left(=\frac{14}{75}\right), 0.187[0.186,0.187]$

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SL 4.11—Formal conditional probability question 1