Question

321:9::512:15::841:40::751:?

Answer 1

Very Interesting Question  !!!. Thanks for asking .

Solution:
The correct answer is 751 :42

Explanation :

Please follow the following sequence :

321= 3 x (2 + 1 ) =3x3 =9

512 = 5 x ( 1 + 2) = 5x (3) =15

841 = 8  x (4+1) = 8x 5 =40

751 = 7 x (5+1) =7 x 6 =42

Hence the answer is 42

Answer 2

guess '?' is x

so,321/9=512/15=841/40=751/x
or, 107/3=512/15=841/40=751/x
or, 107=512=841/8=751/x [ ∵15/3=5 & 40/5=8 ]
or, 107=512=841x=6008 [ ∵ 751*8=6008 ]
or, 841x=6008-512-107=5389
or, x = 5389/841 = 6.41 [approx ]
or,