KöMaL 2007 K139

Replace each circle between the numbers by the symbol of one of the basic operations so that the result is 100. (Note that brackets are not allowed.) $1\ \circ \ 2\ \circ \ 3\ \circ \ 4\ \circ \ 5\ \circ \ 6\ \circ \ 7\ \circ \ 8\ \circ \ 9 = 100$