Transcript Probability Trees

A very good way of working out
complicated probability problems is
to draw them.
The best way of drawing them is to
make a probability tree.
On a probability tree, lines split to show
the different possible results.
You label the ends of the lines with what
could happen.
You label the middle of each line with
the probability of each happening.
This is the probability tree for
flipping one coin.
Each split adds up to
1 for fractions
1 for decimals
100% for percentages
If you are drawing a tree for more
than one thing, like rolling two dice,
you tree will have two splits. One
split after the other.
The probability tree is like a maze. You choose
a path through it to get the results you want.
Start on the left and move along the lines
until you get to the right.
To find the probability of those results
multiply the numbers on the lines you use.
If more than one path gets you what you want
then add up the results.
Chance of 2 Heads =
Chance of 2 Tails =
Chance of 1 of each =
The probability tree shows the
chances of different combinations
when you flip a coin and then draw a
card to see if it is a picture card.
In a deck of cards there are 16
picture cards out of 52.
Sometimes the probabilities will
change depending on what the first
result is.
e.g.
You have a drawer with 10 socks in it,
7 red and 3 black. You draw out two
socks, one at a time.
e.g.
You have a drawer with 10 socks in it,
7 red and 3 black. You draw out two
socks.
What is the chance you draw out;
a) 2 Red Socks
b) 2 Black Socks
c) 1 Red Sock and 1 Black Sock
You have a bag with a bunch of coins in
it. There are four $2 coins and six $1
coins.
Draw a probability tree showing two
coins drawn out at random.
What is the chance of drawing out a total
of; a) $2
b) $3
c) $4
You have a bag with a bunch of coins in it.
There are four $2 coins and six $1 coins.
Draw a probability tree showing three coins
drawn out at random.
What is the chance of drawing out a total of;
a) $3
b) $4
c) $5
d) $6
Lotto strike requires you to get the first four
balls drawn in order. The balls are numbered
from 1 to 40.
Draw a probability tree to show the chance of
winning lotto strike. There will be ___ splits
and each split will be between “Right
Number” and “Wrong Number”.
Make your probability tree big.