1) 612:18 =1:1,then the original ratio of 30 plus 60 is established, or the original ratio of 90 minus 60 is also established.

2)6/3=2, 4.8/3= 1.6, and the area =1.6x2 = 3.2cm2.

3)5m=500cm, 500x 1:500= 1cm, area = τ r2 = 3.14x12 = 3.14.

4) 1.5x3000=4500cm=45m, 3x3000=6000cm=60m, area = 60x45 = 2700.