Final answer:
Using the scale provided of 3 cm to 7 km, a road that is 12 cm long on the map corresponds to a real-life distance of 28 km.
Step-by-step explanation:
To calculate the real-life distance represented by the 12 cm road on the map, we can set up a proportion based on the given scale of 3 cm to 7 km. The proportion is as follows:
3 cm : 7 km = 12 cm : X km
To find the value of X, we cross-multiply and solve for X:
(3 cm) × (X km) = (12 cm) × (7 km)
X × 3 cm = 84 cm×km
X = 84 cm×km / 3 cm
X = 28 km
Therefore, the road in real life is 28 km long, which corresponds to answer option (c).