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How likely is it that it's going to rain today? What is the chance you will go to school tomorrow? How likely is it you will ace your next maths test?
(Seems like very likely with all the studying you are doing now!)
The chance of something happening, i.e. how likely it is, is called probability.
We usually write it as a fraction as that's how we calculate it!
On the top (numerator) of the fraction, we place the number of desired outcomes, i.e. what we are calculating the probability of.
(We call them 'desired' in maths even if you might not like it actually happening - like it raining today!)
On the bottom (denominator) of the fraction, we place the number of all possible outcomes, i.e. how many possible options there are altogether.
Let's have a look at an example. How could we calculate the probability of selecting a yellow card at random from the following cards?
There are four yellow cards (the cards we are calculating the probability of getting!) so the number of desired outcomes is 4.
There are six cards altogether, so there are 6 possible outcomes.
The probability of choosing a yellow card is 4/6 which we can then simplify to 2/3.
(Normally, 4/6 is accepted in an exam unless the question asks for the answer to be a fraction in its simplest form. But if we want to be proper mathematicians, we should always simplify anyway!)
Ready to have a go at some questions?
