Answer
The circumference of the circle is $5.7$ km.
Work Step by Step
1. Find the diameter of the circle
$= 0.9 \times 2$
$= 1.8$ km
2. Using the formula $= diameter \times \pi$, find the circumference
$= 1.8 \times 3.14$
$= 5.652$ km
$= 5.7$ km
