Select the option that is related to the fourth number in the same way as the first number is related to the second number and fifth number is related to sixth number.

15: 210 :: ? : 90 :: 20 : 380

10

15: 210 :: ? : 90 :: 20 : 380

The logic;

( First no. x first no. -1 = =Second number)

15 : 210

15 x 15-1

210

20 : 380

20 x20-1

380

Similarly,

? : 90

10 x10-1

90