The perimeter equals 10.5 cm.
If the smallest side is 3cm, that means that there are two sides that equal 3cm because the third side is larger, so it can't be the smallest. This means we know that the third side must equal 3 × 1.5 = 4.5.
Now we just need to add up all the side lengths, which gives us 3 + 3 + 4.5 = 10.5
I hope this helps!
