Question Number 136000 by physicstutes last updated on 17/Mar/21
$$\mathrm{A}\:\mathrm{room}\:\mathrm{has}\:\mathrm{5}\:\mathrm{doors},\:\mathrm{if}\:\mathrm{a}\:\mathrm{person}\:\mathrm{enters}\:\mathrm{through}\:\mathrm{a}\:\mathrm{dooor}, \\ $$$$\mathrm{that}\:\mathrm{person}\:\mathrm{cannot}\:\mathrm{leave}\:\mathrm{through}\:\mathrm{that}\:\mathrm{same}\:\mathrm{door}.\:\mathrm{Find}\:\mathrm{the}\:\mathrm{number}\: \\ $$$$\mathrm{of}\:\mathrm{ways}\:\mathrm{that}\:\mathrm{person}\:\mathrm{can}\:\mathrm{enter}\:\mathrm{and}\:\mathrm{leave}\:\mathrm{that}\:\mathrm{room}. \\ $$
Answered by liberty last updated on 17/Mar/21
$$\mathrm{5}×\mathrm{4}=\mathrm{20} \\ $$