Total number of defected radios is 18
Let the total number of defective radios be taken as y
If 0.024% of the total number of radios inspected are defective, i.e 0.024% of y
[tex]\frac{0.024}{100}y=18[/tex]Solve for y, by cross multiplying
[tex]\begin{gathered} \frac{0.024}{100}y=18 \\ 0.024y=18\times100 \\ \text{Divide both sides by 0.024} \\ \frac{0.024y}{0.024}=\frac{1800}{0.024} \\ y=75000 \end{gathered}[/tex]Hence, the number of radios inspected, y, is 75000