# Permutations and Combinations 1 (Counting principle) | Summary and Q&A

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May 18, 2017
by
tecmath
Permutations and Combinations 1 (Counting principle)

## TL;DR

Learn how to quickly count the number of different combinations and permutations using the counting principle.

## Key Insights

• 🔄 The counting principle simplifies the process of counting combinations and permutations.
• 🌲 Tree diagrams can be used to visualize all possible combinations, but they can be time-consuming to draw.
• #️⃣ By multiplying the number of choices for each category, the total number of possibilities can be determined quickly.
• 🖐️ The counting principle can be used in various scenarios, such as choosing outfits, creating menus, playing the lottery, or designing license plates.
• 👻 The counting principle allows for more efficient calculations and can handle larger numbers of choices.
• 👻 In scenarios where no repeats are allowed, the counting principle is adjusted by reducing the number of choices for subsequent categories.
• 🛟 The counting principle is a fundamental concept in combinatorics and is applicable in many real-life situations.

## Transcript

good day welcome to Tech math Channel what we're going to be having a look at in this video is the counting principle and this is a way of counting up our various combinations really really quickly so this is the start of a series of videos where we're going to be looking at combinations and permutations which is pretty much a a nice mathematical w... Read More

### Q: What is the counting principle?

The counting principle is a technique that simplifies counting the number of combinations or permutations. It involves multiplying the number of choices for each category to determine the total number of possibilities.

### Q: How is the counting principle used in the example of choosing outfits?

In the example, there are 2 choices for shoes, 2 choices for pants, and 3 choices for shirts. By multiplying these numbers together (2 * 2 * 3), we find that there are 12 different combinations of outfits.

### Q: Can the counting principle be applied to menus and restaurant orders?

Yes, the counting principle can be used to calculate the number of different combinations for a three-course dinner. In the example given, with 4 choices for the entre, 10 choices for the main course, and 3 choices for dessert, there are 120 different combinations possible.

### Q: How can the counting principle be used for a lottery scenario?

For a lottery with 6 numbers chosen from 45, the counting principle can be applied. Starting with 45 possibilities for the first number, each subsequent number decreases by one. By multiplying these numbers together, we find that there are 5,864,443,000 different combinations.

## Summary & Key Takeaways

• The counting principle is a method for quickly determining the number of different combinations or arrangements of items.

• In the video, the counting principle is applied to various scenarios, such as arranging books on a shelf and choosing outfits.

• A tree diagram is used to visualize all possible combinations, but the counting principle allows for a faster calculation by multiplying the number of choices for each category.