Is 40% alcohol 2.5% stronger or 6.666’% stronger than 37.5% alcohol?

Question

So I’ve always considered myself fairly competent at maths and this has absolutely stumped me.

Initially my brain says obviously 40% alcohol is 2.5% stronger than 37.5% alcohol, but 2.5 is 6.666’% of 37.5, so is 40% alcohol actually 6.666’% stronger than 37.5% alcohol?

Someone help me I feel like I’m going mad

In: Mathematics

Answer 1

You are doing percentages of percentages which is where you are having problems. 1 litre of 37.5% alcohol has 15 units of 2.5% alcohol whereas a litre of 40% alcohol has 16 units of 2.5% alcohol. So you need the difference between 15 and 16 for a percentage difference.