2*pi*1.4km

The easiest way to solve this is to to do 2*pi first.

$${\mathtt{2}}{\mathtt{\,\times\,}}{\mathtt{\pi}} = {\mathtt{6.283\: \!185\: \!307\: \!179\: \!586\: \!5}}$$

Now, multiply 6.2831853071795865 by 1.4 km.

$${\mathtt{6.283\: \!185\: \!307\: \!179\: \!586\: \!5}}{\mathtt{\,\times\,}}{\mathtt{1.4}}{km} = {\mathtt{8.796\: \!459\: \!430\: \!051\: \!421\: \!1}}{km}$$

So, $${\mathtt{8.796\: \!459\: \!430\: \!051\: \!421\: \!1}}{km}$$ Is the answer.