What is the probability of rolling
an odd number on an ordinary fair dice? Circle Your answer.
Well, for this question, what we’re
trying to do is work out the theoretical probability of rolling an odd number on an
ordinary fair dice. And it’s theoretical because we’re
not doing any trials, we’re not experimenting by rolling the dice, we’re just
calculating the probability. And to work out theoretical
probability, what it’s equal to is the number of desired outcomes, so in this case
the number of odd numbers, divided by the total number of possible outcomes, so in
this case the total number of numbers on our dice.
So therefore, we can say the
probability of an odd number, and I’ve used probability notation here, so we’ve got
𝑃 then a bracket with odd inside. And this is gonna be equal to,
well, it’s gonna be equal to the number of desired outcomes to the number of odd
numbers. Well, if we look at the numbers on
an ordinary dice, we’ve got one, two, three, four, five, six. So, we’ve got three odd numbers
cause we got one, three, and five. So, that’s gonna be three. And this is gonna be over the total
number of possible outcomes. We’ll consider there are six
possible outcomes because, as we’ve already said, it’s one, two, three, four, five,
or six. So therefore, we could say the
probability of rolling an odd number on an ordinary fair dice is three over six.
But hold on. Three over six is not one of the
answers. So, what do we need to do now? Well, we need to simplify our
fraction. And to simplify our fraction, one
way of doing this is by looking at the numerator and denominator and finding a
common factor, in fact the highest common factor. And we can see that the highest
common factor of three and six is three.
So, we divide the numerator and
denominator by three, which is gonna give us one-half, or one over two. And that’s because three divided by
three is one, and six divided by three is two. We also could’ve seen that it was
gonna be a half because three is half of six. So therefore, we can say that the
probability of rolling an odd number on an ordinary fair dice is a half. And I have circled the fourth
answer, which is our correct answer.