Answer: Equal amounts of the wrong drink in each – Crucially, the two cups have equal amounts of liquid before and after the mixing. Without needing to do the algebra you can argue that if one cup contains 90% tea and 10% coffee, the other 10% of tea must be mixed with the other 90% of coffee because the percentages of each drink must add to 100.

“You progress further on your journey”

Alice and Bob have a 100-metre race. Alice crosses the line when Bob has only reached the 90m mark. They race again but with Alice starting 10m behind Bob. Who will win?

Alice

Bob

It will be a tie