Question Number 160665 by mr W last updated on 04/Dec/21
$${In}\:{how}\:{many}\:{ways}\:{can}\:{you}\:{divide}\:\mathrm{20} \\ $$$${students}\:{into}\:\mathrm{5}\:{groups}\:{with}\:\mathrm{4}\:{students} \\ $$$${in}\:{each}\:{group}\:{such}\:{that}\:{any}\:{two} \\ $$$${students}\:{don}'{t}\:{meet}\:{each}\:{other}\:{in} \\ $$$${more}\:{than}\:{one}\:{group}. \\ $$
Commented by talminator2856791 last updated on 06/Dec/21
$$\:“\mathrm{don}'\mathrm{t}\:\mathrm{meet}''\:\mathrm{mean}? \\ $$
Commented by mr W last updated on 06/Dec/21
$${it}\:{means}\:{they}\:{are}\:{not}\:{together}\:{in}\:{the} \\ $$$${same}\:{group}\:{for}\:{more}\:{than}\:{one}\:{time}. \\ $$$${i}.{e}.\:{you}\:{may}\:{not}\:{put}\:{any}\:{two}\:{students} \\ $$$${in}\:{the}\:{same}\:{group}\:{more}\:{than}\:{one}\:{time}. \\ $$