IMSO 2014 — Math Division — Short Answer Question 25

Let $ABC$ be a triangle such that $AB=1$ cm and $BC=1.5$ cm. $D$ is a point on the line through $A$ parallel to $BC$, such that $CD=4$ cm. Write down all possible integral values of the length, in cm, of $AD$.

Answer entry (editorial guidance): Enter the numbers in ascending order, separated by commas, without units.