9 is also a possible answer,
series given → 81 , 54 ,36 , 24
difference between first two terms( 81 – 54 = 27) then (54 – 36 = 18) then (36 – 24 = 12) see
27 = 3 * 9
18 = 3 * 6
12 = 3 * 4
now take 9 , 6 , 4
difference between first two (9 – 6 = 3) then (6 – 4 = 2) so whats the next term?
it will be 1 right?
so means missing term will be 3 *3.
please check if anything is incorrect! not sure about this !