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Q. Find the missing number, if the same rule is followed in three figures.

Hi, 
Here see the diagram how terms are multiplied and 


So in 584 
5 = 1 x 5 product of middle two numbers 1 and 5 
8 = 2 x 4  product of 2 and 4 as mentioned in the diagram 
4 = 2 x 2 remaining two numbers product

and in next number 
694 
6 = 3 x 2 
9 = 3 x 3 
4 = 2 x 2 

so in the missing number 

= 678