Select the set in which the numbers are related in the same way as are the numbers of the following sets.

(NOTE: Operations should be performed on the whole numbers, without breaking down the numbers into its constituent digits. E.g. 13 – Operations on 13 such as adding/deleting/multiplying etc. to 13 can be performed. Breaking down 13 into 1 and 3 and then performing mathematical operations on 1 and 3 is not allowed.)

(10, 20, 4)

(15, 30, 6)

The correct option is (20, 40, 8).

Let's analyze the relationship between the numbers in the given sets: (A, B, C).

First set: (10, 20, 4)
We can observe the following pattern:
$B=2\times A$
$20=2\times 10$
And for the third number:
$C=\frac{A\times B}{50}=\frac{10\times 20}{50}=\frac{200}{50}=4$ (Alternatively, $C=\frac{2\times A}{5}=\frac{2\times 10}{5}=4$).

Second set: (15, 30, 6)
Checking the same logic:
$B=2\times A$
$30=2\times 15$
And for the third number:
$C=\frac{A\times B}{50}=\frac{15\times 30}{50}=\frac{450}{50}=6$ (Alternatively, $C=\frac{2\times A}{5}=\frac{2\times 15}{5}=6$).

Now, let's test the given options to find which set follows the same pattern:

Testing option (20, 40, 8):
Here, A = 20, B = 40, C = 8.
1. $B=2\times 20=40$ (Satisfied)
2. $C=\frac{20\times 40}{50}=\frac{800}{50}=16$... wait, using $C=\frac{2\times A}{5}=\frac{2\times 20}{5}=8$ (Satisfied).

Hence, the set (20, 40, 8) follows the exact same relationship as the given sets.