To solve for the length of the longest side of the triangle in Jordan's scale drawing, we first determine the scale factor used for the drawing. Since the original side measuring 6 cm is scaled up to 24 cm, we can calculate the scale factor as follows:
\[ \text{Scale Factor} = \frac{\text{New Length}}{\text{Original Length}} = \frac{24 \text{ cm}}{6 \text{ cm}} = 4 \]
This means that the lengths of all sides of the triangle in Jordan's scale drawing are 4 times the lengths of the original triangle.
Next, we identify the original longest side of the triangle. Since we don't have the actual measurements of the original sides, let's assume the longest side of the original triangle was \( x \) cm.
In this case, the length of the longest side in the scale drawing would be:
\[ \text{Longest Side in Scale Drawing} = x \times 4 \]
To determine which answer choice may correspond to the scaled longest side, we need to find \( x \):
- If the original longest side \( x \) was, for example, 5 cm, the scaled longest side would be \( 5 \times 4 = 20 \) cm.
- If \( x \) was 7 cm, scaled version would be \( 7 \times 4 = 28 \) cm.
- If \( x \) was 1 cm or 2 cm, scaled versions would not match the remaining answer choices.
Among the answer choices given:
- 1.75 cm
- 28 cm
- 4 cm
- 20 cm
The correct calculation shows the longest side in the scaled drawing could only be 20 cm or 28 cm depending on the original longest side \( x \).
Given that the question does not specify the original longest side, but knowing Jordan's scale drawing is a scaled version, we conclude appropriately.
Thus, based on common translatable values, the correct answer would be:
20 centimeters.