Mathematics · a topic
Permutations and combinations, Taught not just answered.
A real-time, 1:1 lesson on Permutations and combinations: an AI teacher explains it out loud while it visualizes every step. Interrupt it, ask why, and it checks you got it, in 26 languages.
The idea
What is Permutations and combinations?
Permutations and combinations are systematic ways to count arrangements and selections without listing them. A permutation counts ordered arrangements, so choosing three medallists from eight runners gives eight times seven times six possibilities. A combination counts unordered selections, so it divides out the number of ways the chosen items could be reordered, giving the binomial coefficient n choose r. Both rest on the multiplication principle: when a task has independent stages, multiply the number of options at each stage.
Where it appears: Class 11 CBSE, A-level, IB Mathematics, AP Statistics, JEE, CAT and GMAT, discrete mathematics courses.
Where learners get stuck
Why Permutations and combinations is hard
The single hardest step is deciding whether order matters in a word problem; learners also forget to divide by repeated letters in words like ASSESS or to handle restrictions such as two people who must sit together.
The picture a good explanation starts with: A row of empty slots filled in sequence with shrinking option counts beneath each, then the same picture with identical selections grouped to show division by r factorial.
A lesson, step by step
How a lesson on Permutations and combinations goes
01
Ask
Type or say "How do I tell if a question needs order or not?" in your own words, in any of 26 languages.
02
Plan
The tutor plans a storyboard, one picture per idea, starting with a row of empty slots filled in sequence with shrinking option counts beneath each, then the same picture with identical selections grouped to show division by r factorial.
03
Explain
It explains Permutations and combinations out loud while the picture builds step by step, pitched to your level (Class 11 CBSE and up).
04
Interrupt
Say "wait, why?" or type a doubt: it stops, answers over the picture, and carries on. Ask for a different explanation any time.
05
Check
A checkpoint question makes sure the idea landed, and Tests keep the practice going.
06
Your notes
Upload a PDF or a photo of your class notes or a past paper and the lesson follows your textbook's terms.
Ask it anything
Questions learners ask about Permutations and combinations
- How do I tell if a question needs order or not?
- Why do we divide by r factorial in combinations?
- How many ways can the letters of a word be arranged?
Any of these, or your own, typed or spoken. The tutor answers on the picture and adapts to how well you are following.
Questions
Asked, Answered
Can LetMeTeach explain Permutations and combinations?
Yes. Ask in your own words and the tutor plans a lesson on Permutations and combinations: it starts with a row of empty slots filled in sequence with shrinking option counts beneath each, then the same picture with identical selections grouped to show division by r factorial. Then it explains each step out loud as the picture builds, stops when you say "wait, why?", and ends with a checkpoint question.
Where does Permutations and combinations come up?
Class 11 CBSE, A-level, IB Mathematics, AP Statistics, JEE, CAT and GMAT, discrete mathematics courses. The lesson is pitched to your level and the exam or curriculum you follow, and you can upload your own notes or past papers so it uses your textbook's terms.
Can I learn Permutations and combinations in my own language?
Yes. LetMeTeach teaches in 26 languages and plans the lesson in the language you choose rather than translating an English one, so the terms match what your textbook says. The Free plan includes 7 hours a month with no card.
Last updated
Learn Permutations and combinations, Starting now.
Ask "How do I tell if a question needs order or not?" and watch the answer drawn. The Free plan needs no card.