Convert both quantities to the same unit, then simplify the ratio.<br><br>
&bull; 1.5 kg = 1500 g<br>
&bull; Ratio 45 g : 1.5 kg = 45 : 1500<br>
&bull; Simplify: divide both by their HCF. 45 and 1500 are both divisible by 15.<br>
&bull; 45 ÷ 15 = 3, 1500 ÷ 15 = 100<br>
&bull; Ratio = 3 : 100<br><br>
Final Answer: 3:100