To express a compound length as a decimal in metres, convert the centimetre part to metres by dividing by 100, then add.<br><br>
&bull; 50 cm = 50 ÷ 100 = 0.5 m<br>
&bull; 3 m + 0.5 m = 3.5 m<br><br>
Final Answer: 3.5 m