Solve without a calculator – 1

$55\times 1.609$ nearly equals $(\dfrac {100}{2}+ \dfrac {10}{2})\times 1.61 = \dfrac {(161 + 16.1 )}{2} = 88.55$

$ANSWER:[88.55] = \boxed {89}$

One mile corresponds to $1.609344$ kilometers, which is close to the golden ratio $\phi \approx 1.618$ . $\phi$ also happens to be the ratio between consecutive Fibonacci numbers and fortunately, $55$ is a Fibonacci number. To convert into kilometers, just take the next Fibonacci number which is $89$ .