9514 1404 393
Answer:
4.2 km
Step-by-step explanation:
The altitude of the triangle can be found using the triangle area formula:
A = 1/2bh
22.7 km² = 1/2(10.8 km)h
h = (22.7 km²)/(5.4 km) ≈ 4.2037... km
The missing measurement is about 4.2 km.
