My father's desk is 200mm long and mine measures 1900mm how much longer is my father's desk write your answer in cm

We know that 1 cm = 10 mm.

Father's desk length:
200 mm = 200 / 10 cm = 20 cm

My desk length:
1900 mm = 1900 / 10 cm = 190 cm

My father's desk is 20 cm long.
My desk is 190 cm long.
Since 20 cm is less than 190 cm, my father's desk is shorter than your desk.

Difference = Length of my desk - Length of father's desk
Difference = 190 cm - 20 cm = 170 cm

My father's desk is not longer than your desk; it is 170 cm shorter.