PROBLEMA NUM: 5004 - CATEGORIA: mcd-mcm - DIFFICOLTA': ***

Reid and Trisha are using a balance in science class. On his side, Reid places metal rings that weigh 5 kilograms each. On the other side, Trisha places metal blocks that weigh 10 kilograms each.
What is the smallest number of kilograms Reid and Trisha could each place on their side to make the two sides equal?