Length of a scale = 30 cm
Thickness of a scale = 5mm
To find their ratio let us first make their units equal .
30 cm = 30 × 100 mm = 300 mm
Length of a scale = 300 mm
Thickness of a scale = 5 mm
Ratio of thickness of scale to length of scale =
= 5 : 300 = 5/300
Let us simplify 5/300 by dividing it's numerator and denominator by 5 .
= 5 ÷ 5 / 300 ÷ 5
= 1/60
= 1 : 60 mm
Therefore , the ratio of the thickness of scale to the length of scale is 1 : 60 mm .