Quantitative Reasoning

A 12 % (w/v) solution means 12 g of drug per 100 ml, so for 250 ml the drug mass is 0.12 × 250 = 30 ml, and with a density of 1 g/ml this equals 30 g, making answer B correct. A typical trap is to apply the 12 % to only 200 ml (12 % × 200 = 24 g) or to interpret the percentage as 12 g total, which yields the distractor 25 g, both misreading the proportion.

Each 10 ml costs £4, giving a unit price of £4 ÷ 10 ml = £0.40 per ml; multiplying by the required 35 ml yields £0.40 × 35 = £14, so answer B is correct. A common mistake is to scale the price for 30 ml (3 × £4 = £12) and then add another £4, which gives £16, or to forget the proportional increase, leading to the distractors £12 or £16.

A period of 9 months contains three 3-month intervals, meaning the initial value doubles three times, which equals 8 times the start. A diagram for this topic isn't available yet — the worked example below walks the same reasoning step by step.

• !Option C is incorrect because it assumes a linear increase of 2 times per interval rather than exponential growth.
• !A common mistake is to scale the price for 30 ml (3 × £4 = £12) and then add another £4, which gives £16, or to forget the proportional increase, leading to the distractors £12 or £16.
• !A typical trap is to apply the 12 % to only 200 ml (12 % × 200 = 24 g) or to interpret the percentage as 12 g total, which yields the distractor 25 g, both misreading the proportion.
• !A common error is to treat the raw increase of 24 bpm as a 24 % change, ignoring that percentages are relative to the starting value, which leads to distractor A.

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