Flashcards
Statistics - nCr and nPr
Cards in this deck (7)
- 1nCrFormula:
n! / r!(n-r) - 2Example7C2 = 7! / 2! 5!
- 3nPrFormula;
n! / (n-r)! - 4Example5P3 = 5! / 2!
- 5NotesFor nCr, order is not important whereas with nPr order is important.
- 6QuestionIn a group of 30 pupils, 20 are girls and 10 are boys. From these 30 pupils, 5 are chosen at random.
(i) How many ways can this be done?
(ii) Find the probability there are exactly 3 girls chosen - 7Answers(i) 30C5 = 142506
(ii) 20C3 x 10C2 = 51300
Probability = 51300 / 142506
= 0.3
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- A-Level Maths (S1) Flashcards on Statistics - nCr and nPr, created by Liv Coote on 24/03/2016.
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- Liv Coote
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