Factorial method. What is the probability to have two girls and three boys in a family

Factorial ! Example: 4! is shorthand for 4 x 3 x 2 x 1 Factorial Symbol The factorial function (symbol: !) means to multiply a series of descending natural numbers. Examples: 4! = 4 × 3 × 2 × 1 = 24 7! = 7 × 6 × 5 × 4 × 3 × 2 × 1 = 5040 1! = 1 4! is usually pronounced “4 factorial“, but some people even say “4 shriek“ or “4 bang“ Calculating From the Previous Value You can easily calculate a factorial from the previous one: n n! 1 1 1 1 2 2 × 1 = 2 × 1! = 2 3 3 × 2 × 1 = 3 × 2! = 6 4 4 × 3 × 2 × 1 = 4 × 3! = 24 5 5 × 4 × 3 × 2 × 1 = 5 × 4! = 120 6 etc etc Example: What is 10! if you know that 9!=362,880 ? 10! = 10 × 9! 10! = 10 × 362,880 = 3,628,800 So the rule is: n! = n × (n-1)! Which just says “the factorial of any number is that number times the factorial of (1 smaller than that number)“, hence 10! = 10 × 9!, or even 125! = 125 × 124! What About “0!“ Zero Factorial is interesting ... it is generally agreed that 0! = 1. It may seem funny that multiplying no numbers together gets you 1, but it helps simplify a lot of equations. Where is Factorial Used? Factorials are used in many areas of mathematics, but particularly in Combinations and Permutations #genomics #locus #GeneStructure #phenotype #eukaryotic #genetics #Cancer #chromosomes #GeneticsLecture #DNA #GeneticTesting #prokaryotes #Genetics101 #alleles #genomes #dnaMolecule #geneExpression #Allele #RNA #proteins #GeneticExamQuestionsSolutions #molecularBiology #protein #precalculus #basicIntroduction #howToSimplifyFactorialExpressions #howToAddAndSubtractFactorials #howToEvaluateFactorialExpressions #howToMultiplyAndDivideFactorials #algebraicExpressions