First of all, here is the formula that solves ALL probability problems.
Memorize this:
Probability =
(number of different successful possibilities)
divided by
(total number of all possibilities).
At the beginning, the pencil bag contains (24 + 15 + 8) = 47 pencils.
The first pencil Carrie will pull out is for her friend. What's the probability
that it will be a blue one ?
There are 15 blue pencils in the bag, so out of the 47 total possible results,
15 of them would be successful.
So the probability of pulling a blue one is 15/47 .
Now, after that, she wants to pull out a red one for herself. Notice that
there are only 46 pencils in the bag now. And 24 of them are red. So
the probability of pulling a red one is 24/46 .
The probability of BOTH events being successful is the product
(15/47) x (24/46) .
It's time to pull out the calculator.
(15/47) x (24/46) = 360/2162 = 0.1665 = 16.65% (16.7%)
