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Question Number 177040 by cortano1 last updated on 30/Sep/22

Answered by mr W last updated on 30/Sep/22

$$totalnumberof9-digitnumbersis:$$$$9!=362880$$$$$$$$numberofthosewhicharedivisible$$$$by4is:$$$$lastdigitis2:$$$$\mathrm{xxxxxxx}12/32/52/72/92\Rightarrow 5\times 7!$$$$lastdigitis4:$$$$\mathrm{xxxxxxx}24/64/84\Rightarrow 3\times 7!$$$$lastdigitis6:$$$$\mathrm{xxxxxxx}16/36/56/76/96\Rightarrow 5\times 7!$$$$lastdigitis8:$$$$\mathrm{xxxxxxx}28/48/68\Rightarrow 3\times 7!$$$$\mathrm{\Sigma }:16\times 7!=80640$$

Commented by cortano1 last updated on 30/Sep/22

$$\mathrm{why}\mathrm{sir}\mathrm{last}\mathrm{digit}\mathrm{is}2=4\times 7!?$$

Commented by mr W last updated on 30/Sep/22

$$ihadsometypos.nowfixed.$$

Commented by Tawa11 last updated on 03/Oct/22

$$\mathrm{Great}\mathrm{sir}$$

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