Any question answered...

You are reading a single comment by @duncs and its replies. Click here to read the full conversation.

•

hugo7
3 people may or may not send me a Xmas card.
1. What is the search term/field(?) of maths I need to be Googling?
2. What's the formula for checking my possible combinations are correct?
Sort of like:
- Alfred sends letter, Bob doesn't, Charlie doesn't
- Alfred sends letter, Bob sends letter, Charlie doesn't
- Alfred sends letter, Bob sends letter, Charlie sends letter
  Etc.

•

duncs in reply to @hugo7

combinations and permutations pretty much covers it
If you wanted to check how many combinations there were when, say, 3 from 10 sent you a card
then from a 'n, choose r' type calc then n=10, r=3 and the number of combinations would be 120
https://www.calculatorsoup.com/calculators/discretemathematics/combinations.php

in your example, if you just have two choices then you'd probably most often find it illustrated as a binary tree 3 levels deep

•

hugo7 in reply to @duncs

Cheers.

Yes, it's just 3 options each yes or no.

Ie what are all the combinations of those three either sending or not sending me a card.

I found something referencing the n and r, but didn't understand how to apply it. n = names of people sending me cards, right?
But then how does r fit in?

When I write them in a table I get 18 entries, but I'd like to verify that, and also have more knowledge for the future if I come across a bigger number of options.

About

@duncs started