For many working parents, there is no single solution to their child-care needs. More than a third use more than one option, such as day-care centers part of the time and friends, neighbors or relatives on other occasions. A recent study conducted by the Urban Institute, a nonprofit policy research organization, revealed that about 30 percent of working parents have two child-care arrangements, and another 8 percent are using at least three. The study found that 65 percent of parents juggling multiple child-care arrangements use a combination of formal day-care centers, Head Start programs, and baby-sitting by relatives and friends. Another 20 percent use two separate day-care centers.