Frequency trees
The Maths Habit Handout to print
How could you sort everyone in this room into two groups?
Now split each group into two again.
- Frequency tree
- A diagram that sorts a group into smaller groups and shows how many are in each.
What do you notice about the numbers?
Each pair of branches adds up to the box before
50 people are at a gym. 30 are members. 21 of the members swim. 8 of the others swim.
64 students: 28 do art. 16 of the art students do music. 9 of the others do music. Find the probability that a student does music but not art.
70 people: 30 are adults. 12 adults and 10 children wear glasses. Find the probability that a person chosen at random wears glasses. 2270
90 people: 50 are men. 35 men and 28 women drive. Find the probability that a person chosen at random does not drive. 2790
70 people: 30 are adults. 12 adults and 10 children wear glasses. Find the probability that a person chosen at random wears glasses. 2270
48 students: 20 study French, the rest Spanish. 14 French and 21 Spanish students pass. Find the probability that a student passes. 3548
70 people: 30 are adults. 12 adults and 10 children wear glasses. Find the probability that a person chosen at random wears glasses. 2270
80 dogs: 35 are puppies. 14 puppies and 27 adult dogs win a rosette. Find the probability that a dog chosen at random wins a rosette. 4180
70 people: 30 are adults. 12 adults and 10 children wear glasses. Find the probability that a person chosen at random wears glasses. 2270
56 visitors: 32 by car, the rest by train. 20 car and 15 train visitors bought lunch. Find the probability that a visitor came by train and did not buy lunch. 956
70 people: 30 are adults. 12 adults and 10 children wear glasses. Find the probability that a person chosen at random wears glasses. 2270
100 seeds: 45 are red, the rest yellow. 38 red and 41 yellow seeds grow. Find the probability that a seed chosen at random does not grow. 21100
Answer sheet
80 people are asked about pets. 35 of them are adults. 14 of the adults and 12 of the children have a dog. How many people have a dog?
28100 people are at a café. The probability that a person chosen at random is a child is 0.35. 20 of the children and 45 of the adults like cheese. How many people do not like cheese?
35
60 people: 25 are adults. 16 adults and 20 children have a pet. Fill in the frequency tree.
35, 9 and 15Find P(has a pet).
3660 = 35Find P(child with no pet).
1560 = 14