Length of paper = 1.2 m

Width of paper = 21 cm

As the units are different we cannot directly take the ratio to take ratio we need to have two quantities with same units

1 m = 100 cm

⇒ 1.2 m = 1.2 × 100 = 120 cm

∴ Length of paper = 120 cm

ratio of width of the paper to its length =

⇒ ratio =

Divide numerator and denominator by 3 we get

⇒ ratio =

Therefore, ratio of width of the paper to its length is 7:40