To express a compound length as a decimal in kilometres, convert the metre part to kilometres by dividing by 1000, then add.<br><br>
&bull; 100 m = 100 ÷ 1000 = 0.1 km<br>
&bull; 10 km + 0.1 km = 10.1 km<br><br>
Final Answer: 10.1 km