If 30 g of 5% ointment is combined with 10 g of 40% ointment what is the percentage strength of the final product?

This percentage represents a much lower concentration than what is possible based on the given ointments. With 30 g of a 5% ointment contributing 1.5 g of active ingredient and 10 g of a 40% ointment contributing 4 g, the combined total of active ingredient significantly exceeds a mere 1.20% strength when divided by the total mass of 40 g.

While this option seems plausible, it does not account for the higher concentration of the 40% ointment. The contributions from both ointments add up to a greater total amount of active ingredient, leading to a final strength that is much higher than 5.50%. A calculation reveals that the total active ingredient is significantly more than what would yield this percentage.

This choice suggests an even higher concentration than possible given the proportions of ointments used. The mixture of 1.5 g from the 5% ointment and 4 g from the 40% ointment only totals 5.5 g of active ingredient, which, when divided by the total mass of 40 g, results in a percentage well below 18.00%.