Explanation

The first thing you need to do is to clean up these expressions. You have 15th, 50th, and decimals, so it is very difficult to compare values.

\(\frac{6n}{15}\) can be reduced to \(\frac{2n}{5}\).
\(0.3n\) is the same as \(\frac{3n}{10}\).

Change your first expression from \(\frac{2n}{5}\) to \(\frac{4n}{10}\).

\(\frac{19n}{50}\) is pretty close to \(\frac{20n}{50}\) or \(\frac{2n}{5}\), the first expression, but a bit smaller.

Because \(\frac{n}{4}\) is clearly the smallest expression and you need only concern yourself with the smallest, the second smallest, and the biggest, you can ignore \(\frac{19n}{50}\).

Convert\(\frac{n}{4}\) to \(\frac{5n}{20}\), and convert your other expressions to 20ths as well.

You now have \(\frac{8n}{15}\), \(\frac{6n}{20}\) and \(\frac{5n}{20}\).

The difference between the smallest and largest is \(\frac{3n}{20}\). Three times the difference between the two smallest is also 3.


The answer is choice C.