The percentage of profit can be calculated by means of the following expression:
![\text{profit}=\frac{\text{sale}-\cos t}{\cos t}*100](https://img.qammunity.org/2023/formulas/mathematics/high-school/m8wq2ym7wkf3mazsqqf7lclfj50gezhrb4.png)
Where the sale is the sale price and cost is the cost at which the article was bought. In this case, the cost is $30 and the sale price is $45. By replacing 30 for cost and 45 for sale into the above expression, we get:
![\text{profit}=(45-30)/(30)*100=(15)/(30)*100=50](https://img.qammunity.org/2023/formulas/mathematics/high-school/fsidpealk3f4ckt1wnub1r7d8nnhy1gxks.png)
Then, the profit percent is 50% (0.5)