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Question Number 13508 by tawa tawa last updated on 20/May/17
$$\mathrm{5}!!\:=\:? \\ $$$$\mathrm{please}\:\mathrm{workings},\:\mathrm{how}\:\mathrm{is}\:\mathrm{the}\:\mathrm{answer}\:\mathrm{15} \\ $$
Answered by mrW1 last updated on 20/May/17
$${n}!!={n}×\left({n}−\mathrm{2}\right)×\left({n}−\mathrm{4}\right)×...×\mathrm{2}\:\:{or}\:\:×\mathrm{1} \\ $$$$ \\ $$$$\mathrm{5}!!=\mathrm{5}×\mathrm{3}×\mathrm{1}=\mathrm{15} \\ $$
Commented by tawa tawa last updated on 20/May/17
$$\mathrm{Now}\:\mathrm{i}\:\mathrm{understand}\:\mathrm{better}.\:\mathrm{God}\:\mathrm{bless}\:\mathrm{you}\:\mathrm{sir}. \\ $$
Commented by RasheedSindhi last updated on 21/May/17
$$\mathrm{Is}\:\mathrm{there}\:\mathrm{any}\:\mathrm{definetion}\:\mathrm{for} \\ $$$$\mathrm{n}!!!\: \\ $$$$\mathrm{Perhaps}\:\mathrm{like}\:\mathrm{this} \\ $$$${n}!!!={n}×\left({n}−\mathrm{3}\right)×\left({n}−\mathrm{6}\right)×...×\mathrm{3}\:\mathrm{or}×\mathrm{2}\:\:{or}\:\:×\mathrm{1} \\ $$$$ \\ $$