The HCF of two numbers is 21 and their LCM is 221 times the HCF.  If one of the numbers lies between 200 and 300, then the sum of the digits of the other number is?

15

HCF = 21                         Numbers → x, y

LCM = HCF × 221

divided HCF

        xy = 221

13 × 17 = 221

   x           y

  13         17

×21       ×21

273        357 → 3 + 5 + 7 = 15