VTMO 2020 — Grade 4 — vtmo Question 8

There are $15$ sticks of length $3 \,\mathrm{cm}$ and $10$ of length $2 \,\mathrm{cm}$. What is the fewest additional $1 \,\mathrm{cm}$ sticks needed to use all sticks as the perimeter of an integer-sided rectangle?