First, let's find the actual length represented by 1mm. Here is the original equation:
3mm = 27km
Divide 3 from both sides of the equation:
1mm = 9km
We have now proven that 1mm is equal to an actual length of 9km. Now multiply the known length of 1mm by 3.5 to find the missing value:
3.5(9) = x
Simplify the left side of the equation:
31.5 = x
We have now proven that 3.5mm is equal to 31.5 km.
I hope this helps!