Multiplication principle of counting for JEE

Formula

\(\text{If a process has successive independent stages with }n_1,n_2,\dots,n_k\text{ choices respectively, then total ways }=n_1n_2\cdots n_k.\)

Variables: \(n_1,n_2,\dots,n_k\) are numbers of choices at successive stages.

Conditions: Each final outcome is formed by choosing one option from each stage.

Core counting in passwords, digit arrangements, distributions, constrained permutations.