Well done to Billie-Jo (Tattingstone School, UK), Rowena, Charlotte and Ross (Stockton) and Timothy, Vincent and Kenneth (Catholic High School, Singapore) for correct solutions.
Four particularly well-presented graphic solutions came from Chris, Michael and someone else from Crofton Junior School, and Daniel (Anglo-Chinese School, Singapore).
This one comes from Rayner (Tao Nan School, Singapore):
$5 + 5 + 2 = 12$ rows