Answer:
16 cm², 49 cm²
Step-by-step explanation:
The area ratio is the square of the perimeter ratio, so is ...
4² : 7² = 16 : 49
As it happens the sum of these "ratio units" is 16 +49 = 65, so each must represent 1 cm².
The areas of the triangles are 16 cm² and 49 cm².