Given the rationale, provide a reasonable question and answer. Step-by-step reasoning process: Hannah = (1 / 2) 18 = 9. 9 + 18 = 27 km. Together they walked 27 kilometers.
 The question and answer:
Nadia walked 18 kilometers, which was twice as far as Hannah walked. How many kilometers did the two girls walk in total?
The answer is 27