Thread: Basic Probability Question

If there are 7 red disks numbered 1 through 7 and 8 yellow disk numbered 8 through 15, find the probability of selecting a disk numbered 3 given that a red disk is selected.


In my little mind I'm thinking this is too easy. There's only one number 3 so it has to be 1 of 15 but that seems too obvious. What am I overlooking? Thanks in advance for any help!

Originally Posted by merccgs12

If there are 7 red disks numbered 1 through 7 and 8 yellow disk numbered 8 through 15, find the probability of selecting a disk numbered 3 given that a red disk is selected.
There's only one number 3 so it has to be 1 of 15 but that seems too obvious. What am I overlooking?

You are overlooking the bit in red.
So the answer is even easier than that it is one in seven.