Answer: 10% – Beginning with the 70% who study Maths, it is only possible for a maximum of 25% of all students to not also study English, leaving a minimum of 45% doing both Maths and English. Repeating this procedure for French and German, we subtract a further 15% then 20%, this leaves 10% who must study all 4.
“You descend further into the maze…”
You begin with two equal cups of tea and coffee. You take a teaspoon of tea and put it in the coffee, then take a teaspoon of the mixture and put it back into the tea. Which original cup contains more of the wrong drink?