Old Order
Who is the youngest in this family?
Age
11 to 14
Challenge level
Problem
Gus is older than Flora.
Alessandro is older than Zara but younger than Flora.
Oliver is younger than Gus but older than Zara.
Yvette is younger than Gus.
Alessandro is older than Oliver.
Flora is younger than Yvette.
Can you list these six friends in order of age?
If you liked this problem, here is an NRICH task which challenges you to use similar mathematical ideas.
Student Solutions
The first sentence tells us that Gus is not the youngest.
The second sentence tells us that neither Alessandro nor Flora is the youngest.
From the third sentence, Oliver is not the youngest, whilst the sixth sentence tells us that Yvette is not the youngest.
So Zara must be the youngest and the order of their ages is Gus, Yvette, Flora, Alessandro, Oliver, Zara.