Final answer:
In a 0.5% dental cartridge of 1.8 ml, there are 9 mg of local anesthetics. This is calculated by converting the percentage into a decimal and multiplying it with the volume of the cartridge, and then converting to milligrams.
Step-by-step explanation:
To calculate the amount of local anesthetic in a dental cartridge, one should multiply the concentration of the solution by the volume of the cartridge. The concentration of 0.5% means that there are 0.5 grams of anesthetic per 100 ml of solution. To make the calculation easier, first convert 0.5% into a decimal, which is 0.005. Then multiply this decimal by the volume of the cartridge expressed in milliliters:
0.005 (percentage in decimal form) × 1.8 ml (volume of the cartridge) = 0.009 grams
To convert grams to milligrams, remember that 1 gram is equal to 1000 milligrams:
0.009 grams × 1000 = 9 mg
Therefore, the correct answer is 9 mg of local anesthetic in the 0.5% dental cartridge.