The ratios are all proportional to 50/1.
Ratios are proportional when its cross products are equal.
a/b = c/d where ad = cb
100/2 is proportional to 50/1 because 1001 = 250 ⇒ 100 = 100
150/3 is proportional to 50/1 because 1501 = 350 ⇒ 150 = 150
175/3.5 is proportional to 50/1 because 1751 = 3.550 ⇒175 = 175
200/4 is proportional to 50/1 because 2001 = 450 ⇒ 200 = 200
