Below is a partial table of the permutations of {a, b, c, d} taking the elements three at a time.

Observe that the total number of permutations is P(n,r)=(n!)/(n-r)!=24

Place the correct permutation for the vacant answer box. Pay special attention to order.

___ bac cab dab
abd ___ cad dac
acb bca ___ dba
acd bcd cbd ___
adb bda ___ dca
adc ___ cdb dcb

Can you please explain on how to do this? I don't what I am even looking at..

Question

Below is a partial table of the permutations of {a, b, c, d} taking the elements three at a time.

Observe that the total number of permutations is P(n,r)=(n!)/(n-r)!=24

Place the correct permutation for the vacant answer box. Pay special attention to order.

___	   bac	   cab	dab
abd	   ___	           cad	dac
acb	   bca	   ___ 	dba
acd	   bcd	   cbd	___
adb	   bda	    ___	dca
adc	    ___	   cdb	dcb

Can you please explain on how to do this? I don't what I am even looking at..