I am thinking of a whole number from 1 to 10.
Then I tell you it is odd.
Is it easier to guess now?
Yes: only 5 numbers are left to choose from
- Conditional probability
- The probability of something, when you already know something else.
- Given that
- Tells you which group to look at.
Given that the student is in Year 7
| Cat | Dog | Total |
|---|
| Year 7 | 12 | 18 | 30 |
|---|
| Year 8 | 14 | 6 | 20 |
|---|
| Total | 26 | 24 | 50 |
|---|
Given that the student is in Year 9.
What goes on the bottom of the fraction?
| Drama | Dance | Total |
|---|
| Year 9 | 14 | 26 | 40 |
|---|
| Year 10 | 16 | 24 | 40 |
|---|
| Total | 30 | 50 | 80 |
|---|
40
Given that the passenger is an adult, find the probability that they chose a window seat.
| Window | Aisle | Total |
|---|
| Adult | 21 | 14 | 35 |
|---|
| Child | 18 | 7 | 25 |
|---|
| Total | 39 | 21 | 60 |
|---|
Look atAdultTotal35
Of these, Window21Probability2135
Given that the student is in Year 11, find the probability that the student cycles.
| Cycle | Walk | Total |
|---|
| Year 10 | 12 | 43 | 55 |
|---|
| Year 11 | 9 | 36 | 45 |
|---|
| Total | 21 | 79 | 100 |
|---|
Look atYear 11Total45
Of these, Cycle9Probability945
Given that the passenger is an adult, find the probability that they chose a window seat.
| Window | Aisle | Total |
|---|
| Adult | 21 | 14 | 35 |
|---|
| Child | 18 | 7 | 25 |
|---|
| Total | 39 | 21 | 60 |
|---|
Look atAdultTotal35
Of these, Window21Probability2135
Given that the drink was sold in the morning, find the probability that it was a hot drink.
| Hot | Cold | Total |
|---|
| Morning | 34 | 16 | 50 |
|---|
| Afternoon | 12 | 18 | 30 |
|---|
| Total | 46 | 34 | 80 |
|---|
Look atMorningTotal50
Of these, Hot34Probability3450
Given that the student chose climbing, find the probability that the student is in Year 8.
| Climbing | Skating | Total |
|---|
| Year 8 | 15 | 21 | 36 |
|---|
| Year 9 | 25 | 19 | 44 |
|---|
| Total | 40 | 40 | 80 |
|---|
(a) Given that it is a van, find the probability that it is electric.
(b) Given that it is electric, find the probability that it is a van.
| Petrol | Electric | Total |
|---|
| Car | 30 | 20 | 50 |
|---|
| Van | 24 | 6 | 30 |
|---|
| Total | 54 | 26 | 80 |
|---|
A youth club has 60 members. 36 are girls. 20 girls and 15 boys play pool. Everyone else plays table tennis. Given that a member plays table tennis, find the probability that the member is a boy.
925Year 10 has 150 students. Given that a student is in Year 10, the probability that they walk to school is 25. How many Year 10 students do not walk?
90
| Bus | Walk | Total |
|---|
| Adult | 12 | 33 | 45 |
|---|
| Child | 18 | 17 | 35 |
|---|
| Total | 30 | 50 | 80 |
|---|
Find P(bus), given that the person is a child.Find P(child), given that the person took the bus.
1830 = 35For an adult, Dev says P(bus) is 12 out of 30. Is Dev right?
No: 1245, out of 45 adults
Exit tickets to print
