Answer:
1/24
Explanation:
To start, we can calculate the probability of each individual event:
Getting the person right:
1/2
Getting the weapon right:
1/3
Getting the room right:
1/4
Here, you're trying to find the probability of the intersection of the three events. This means we must multiply the probabilities of the independent events together.
1/2*1/3*1/4=1/24
or
0.0417
Note that we multiply the probabilities together when the previous event doesn't affect the probability of the next event. In general, questions that ask for the probability of a happening and b happening mean you multiply the probability of a and b (events that satisfy your demands are decreasing because you need BOTH events to occur).
On the other hand, questions that ask for the probability of a or b happening, meaning the events that satisfy your demands will increase (2 options versus 1), so you'd add the probabilities of a and b happening.
Hope that makes sense, let me know if you have any questions!