Two ratios a:b and c:d are said to be proportional, if a/b = c/d or ad = bc.
But in the given ratios 3/4 and 9/16, 3 x 16 ≠ 4 x 9.
Hence, the ratios are not proportional. To make a ratio proportional to another ratio, we just simply multiply both numerator and denominator by same number.
In our given case, student had multiply numerator by 3 and denominator by 4, which is incorrect.
