Find the ratio of 75 cm to 1.5 m.

The given numbers are not in the same units. So, converting them into same units.
1.5 m = 1.5 × 100 cm = 150 cm
[∵ 1 m = 100 cm]

∴ The required ratio is 75 cm : 150 cm
= 75/150
= (75 ÷ 75)/(150 ÷ 75)
= 1/2

∴ Required ratio = 1 : 2