This exercise is a multiple choice questionnaire. For each of the following questions, only one of the four proposed answers is correct. To answer, indicate on your paper the number of the question and the letter of the chosen answer. No justification is required.
A wrong answer, an absence of answer, or a multiple answer, neither gives nor removes points.
The 200 members of a club are girls or boys. These members practice rowing or basketball according to the distribution shown in the table below.
| \cline { 2 - 4 } \multicolumn{1}{c|}{} | Rowing | Basketball | Total |
| Girls | 25 | 80 | 105 |
| Boys | 50 | 45 | 95 |
| Total | 75 | 125 | 200 |
We choose a member at random and consider the following events: $F$ : the member is a girl; $A$ : the member practices rowing.
- The probability of $F$ given $A$ is equal to : a. $\frac { 25 } { 100 }$ b. $\frac { 25 } { 75 }$ c. $\frac { 25 } { 105 }$ d. $\frac { 75 } { 105 }$
- The probability of the event $A \cup F$ is equal to : a. $\frac { 9 } { 10 }$ b. $\frac { 1 } { 8 }$ c. $\frac { 31 } { 40 }$ d. $\frac { 5 } { 36 }$
To get to work, Albert can use either the bus or the train. The probability that the bus breaks down is equal to $b$. The probability that the train breaks down is equal to $t$. Bus and train breakdowns occur independently.
3. The probability $p _ { 1 }$ that the bus or the train breaks down is equal to : a. $p _ { 1 } = b t$ b. $p _ { 1 } = 1 - b t$ c. $p _ { 1 } = b + t$ d. $p _ { 1 } = b + t - b t$
4. The probability $p _ { 2 }$ that Albert can get to work is equal to : a. $p _ { 2 } = b t$ b. $p _ { 2 } = 1 - b t$ c. $p _ { 2 } = b + t$ d. $p _ { 2 } = b + t - b t$
5. We consider a coin for which the probability of obtaining HEADS is equal to $x$. We flip the coin $n$ times. The flips are independent. The probability $p$ of obtaining at least one HEADS in the $n$ flips is equal to a. $p = x ^ { n }$ b. $p = ( 1 - x ) ^ { n }$ c. $p = 1 - x ^ { n }$ d. $p = 1 - ( 1 - x ) ^ { n }$