Given,
Length of rectangular sheet = 1.2 m
= 1.2× 100 cm = 120 cm [∵ 1 m = 100 cm ]
Width of rectangular sheet = 21 cm
Ratio of width to length = 21 cm120 cm
= 740=7:40 [on dividing numerator and denominator by 3]
Hence, the ratio of width of the paper to its length is 7 : 40.