2/3
It is not possible. There is no fraction equivalent to 1/73 which has a denominator less than 50.In fact, if p is any prime greater than 50, then for any fraction q/p, there is no equivalent fraction with denominator less than 50.
any fraction less than 1
a little less than one third. one third is .3333333333333etc.
any fraction where the denominator is larger than 3
2/5
3/8
Yes. 2/3 is 11.1% less than 3/4.
27/100 is one possibility.
Since 100 m is less than 1 km, the relevant fraction has an absolute value less than 1 and so there is no equivalent vulgar fraction.
1/2, a half
17/4
No. The absolute value of the given fraction is less than 1. There is, therefore no sensible way to represent it as an improper fraction.