ï»¿Teacher Sarah stands in front of a big screen.

Teacher Sarah is in her twenties, with straight brown hair in a bob cut. She wears black leggings and a blue Homework Zone T-shirt.

She says HI, TVO KIDS.
I'M TEACHER SARAH.
AND TODAY WE'RE GOING TO
REALLY COOL AND EXCITING
CALLED PROBABILITY.
PROBABILITY REFERS TO THE
LIKELIHOOD OF AN EVENT
HAPPENING OR OCCURING.
THERE ARE TWO TYPES
OF PROBABILITY:
THEORETICAL PROBABILITY AND
EXPERIMENTAL PROBABILITY.
THEORETICAL PROBABILITY
HAS TO DO WITH THE THEORY.
SO, IN THEORY, THE MATHEMATICAL
OR STATISTICAL ODDS
OF AN EVENT OCCURING BASED
ON THE NUMBER OF FAVOURABLE
OUTCOMES AND THE TOTAL
NUMBER OF OUTCOMES.
NOW EXPERIMENTAL PROBABILITY,
THAT HAS TO DO WITH THE
LIKELIHOOD OF AN EVENT
HAPPENING, BASED ON DATA
COLLECTED OR OBTAINED FROM
A SPECIFIC EXPERIMENT.
SO TODAY WE'RE GOING TO
THEORETICAL PROBABILITY.
THE THEORETICAL PROBABILITY
OF PLAYING CARDS.
NOW LET'S SAY YOU WANTED
TO TAKE A REGULAR DECK
OF PLAYING CARDS.
THERE ARE 4 SUITS:
CLUBS AND DIAMONDS.
OUT OF THOSE 4 SUITS, TWO
ARE RED AND TWO ARE BLACK.
THERE ARE ALSO 13
CARDS PER SUIT.
SO SUPPOSE YOU WANTED TO
KNOW, HMM, WHAT ARE THE ODDS
OF RANDOMLY SELECTING A
HEART OUT OF THOSE 52 CARDS?
WELL, IN ORDER TO FIND
THAT OUT, YOU HAVE TO FIND
THE THEORETICAL PROBABILITY.
SO WE NEED TO
KNOW TWO THINGS.
THE FIRST THING WE HAVE TO KNOW
IS THE NUMBER OF FAVOURABLE
OR DESIRED OUTCOMES.
IN THIS CASE WHAT WE
WANT TO KNOW IS HEARTS.
WE ALSO NEED TO KNOW THE
TOTAL NUMBER OF OUTCOMES.
AND IN THIS
CASE IT'S 52
BECAUSE THERE ARE 52
CARDS TO CHOOSE FROM.
SO, AS WE SAID, THE
FAVOURABLE OUTCOME,
THE ONE THAT WE WANT OR THE ONE
WE'RE LOOKING FOR, IS HEARTS.
WE ALSO KNOW THAT
THERE ARE 13 HEARTS
IN A REGULAR
DECK OF CARDS.
SO THE THEORETICAL
PROBABILITY IS THE NUMBER
OF FAVOURABLE OUTCOMES
DIVIDED BY THE TOTAL NUMBER
OF OUTCOMES.
NOW WE CAN JUST
PLUG IN OUR VALUES.
AS WE SAID, WE KNOW THAT
THERE ARE 13 HEARTS
OUT OF THOSE 52 CARDS.
AND 52 CARDS...
IN TOTAL.
SO TO FIND THE THEORETICAL
PROBABILITY, WE ALWAYS START
WITH OUR FORMULA.
THEORETICAL PROBABILITY,
WE CAN USE T.P. FOR SHORT.
THEN WE WRITE OUT THE FORMULA
AND SUBSTITUTE IN OUR VALUES.
SO WE HAD 13 HEARTS, WHICH
IS OUR FAVOURABLE OUTCOME,
AND 52 CARDS IN TOTAL.
NOW WE HAVE TO REMEMBER WE
ALWAYS REDUCE FRACTIONS
TO SIMPLEST FORM.
SO WHAT THAT MEANS IS
WE ARE LOOKING FOR THE
GREATEST COMMON FACTOR
THAT CAN GO INTO BOTH
THE NUMERATOR AND
THE DENOMINATOR.
AND IN THIS CASE OUR
SIMPLEST FORM WOULD BE 1 QUARTER.
WE'RE ALMOST THERE.
SO YOU MIGHT BE ASKING YOURSELF
HOW DO YOU EXPRESS PROBABILITY.
WELL, THERE ARE THREE DIFFERENT
WAYS THAT WE CAN DO THAT.
WE CAN EXPRESS PROBABILITY
AS A FRACTION â€“ 1 QUARTER,
AS A PERCENT, OR
PER HUNDRED... 25 PERCENT,
OR AS A DECIMAL VALUE
BETWEEN ZERO AND ONE.
SO IN THIS CASE OUR DECIMAL
WOULD BE 25 HUNDREDTHS OR 0.25.
ZERO REPRESENTS THE IMPOSSIBLE
AND 1 REPRESENTS CERTAIN.
SO PROBABILITY IS MOST
COMMONLY EXPRESSED AS
A VALUE BETWEEN ZERO AND
ONE, WHICH LETS US KNOW
HOW IMPOSSIBLE OR HOW CERTAIN
AN EVENT IS OF OCCURING.
SO YOU CAN TRY
WHAT IS THE PROBABILITY OF
RANDOMLY SELECTING A CLUB
FROM A REGULAR DECK
OF PLAYING CARDS?
OUTCOMES DIVIDED BY
THE TOTAL NUMBER
OF OUTCOMES.
OR
A HEART?
THIS ONE'S A
LITTLE TRICKY
BECAUSE YOU HAVE TO