Question

Determine the number of permutations of (1,2,3...8) in which exactly four integers are in their natural position​

Answer 1

@N$W€R.

ᴅᴇᴛᴇʀᴍɪɴᴇ ᴛʜᴇ ɴᴜᴍʙᴇʀ ᴏғ ᴘᴇʀᴍᴜᴛᴀᴛɪᴏɴs ᴏғ {1,2,3,4,5,6,7,8,9,10} ᴛʜᴀᴛ ʜᴀᴠᴇ ᴇxᴀᴄᴛʟʏ 3 ɴᴜᴍʙᴇʀs ɪɴ ᴛʜᴇɪʀ ɴᴀᴛᴜʀᴀʟ ᴘᴏsɪᴛɪᴏɴ.

ɦσρε เт'ร ɦεℓρƒµℓ тσ ყσµ!

тнαηk yσυ!