Three of the following number triads are alike in some manner and one is different. Select the odd number triad.
(NOTE: The second and third numbers in the given number triads are formed by performing a certain operation on the first number. The same operation is followed in all the number triads except one. Find that odd number triads.)
1
20 ∶ 400 ∶ 200
2
9 ∶ 81 ∶ 45
3
13 ∶ 169 ∶ 84.5
4
25 ∶ 625 ∶ 312.5