Question

321:9::512:15::841:40::751: the next value will be

Answer 1

2+1=3,3*3=9
1+2=3,3*5=15
4+1=5,5*8=40
5+1=6,7*6=42

Answer 2

His,
In case 1
It's 321
Multiply 1st value (3) with last value (1)=3
Then Multiply first value (3) with second value (2)=6 add both results =9
Therefore 321:9
In case 2
It's 512
In the same way you get result 15
Therefore 521:15
In case 3
It's 841
Multiply 8 with 1=8
Multiply 8 with 4=32
Add both results =40
Therefore 841:40
Now case 4
It's 751
Multiply 7 with 1=7
Multiply 7 with 5=35
Add both of them =42
Therefore 751:42