Question

321:9::532:25::431:16::923:?

Answer 1

321:9::532:25::432:16::923:?

we can write it as

321/9::532/25::432/16::923/?

as we can see that 2nd denominator is sum of first and third

i.e 25=16+9

similarly  3rd denominator  should be and will  be the sum of 2nd and  4th denominator

hence

16=25+?

here we get ?

?=16-25+-9

hence we will put -9 in place of ?