IB Maths AA SL 4.11 Formal Conditional Probability Questions

Practise IB Mathematics SL 4.11 by applying formal conditional probability methods to questions from the Question Bank.

Exam points

Calculate conditional probability with P(A|B) = P(A ∩ B)/P(B), and rearrange to use P(A ∩ B) = P(B)P(A|B) in a stated sample space.
Test independence by comparing P(A|B) with P(A) or P(A ∩ B) with P(A)P(B), interpreting the conclusion in context.

[Maximum number: 2]

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

Figure for Question IB Maths AA SL 4.11 Formal Conditional Probability Questions 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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IB Maths AA SL 4.11 Formal Conditional Probability Questions question 1