Answer:
Light collecting area of 6 mm telescope is 4 times greater than light collecting area of 3 mm telescope.
Step-by-step explanation:
Diameter of 1st telescope = 6 mm
Diameter of 2nd telescope = 3 mm
Light collecting area of telescope is given as

For 1st telescope

For 2nd telescope


Which means light collecting area of 6 mm telescope is 4 times greater than light collecting area of 3 mm telescope.