Daily Dose 040 | Probability and Statistics
How to identify and solve combinations?
Understanding how to quickly identify and solve combinations was always a challenge for me.
However, there was something one of my instructors had said that really stuck with me, it went something like this:
You should think of Combination locks on our lockers as Permutation locks.
For Combinations, the order DOES NOT MATTER.
For Permutations, the order DOES MATTER.
So with this, if our code was 7 21 1 to open our locker, if it was a true Combination lock, then we could put in those numbers in any order!
But they need to be put in that exact order to open, therefore, ORDER MATTERS and it is a Permutation lock! 🙂
For some reason, that always stuck with me.
In this video, we break it all down, showing you exactly how to go about identify and solve combinations faster and with a lot less stress on the FE Exam.
Key Definition
What is a COMBINATION?
A COMBINATION is a selection of objects where the order doesn’t matter.
For example, say we have three balls: one red, one white, and one blue.
If we wanted to see how many different variations of these balls we get after choosing 2 at a time, we find that we get:
red – white
red – blue
white – blue
white – red
blue – red
blue – white
But since order doesn’t matter, red – white and white – red are the same…so that’s a single combination.
This goes for the others as well.
So in reality, instead of 6, there are 3 COMBINATIONS.
From a textbook sense, we would first find the number of PERMUTATIONS (which is 6 for the above scenario) and divide it by the number of ways we can rearrange the PERMUTATIONS…meaning, pair them up as white-blue : blue-white, etc.
So how can we identify and solve Combinations?
Check out the video and see how we can go about solving this type of problem in the most efficient manner.
As always, with Love, Prepineer