某工厂冬季用煤21吨，比计划节约用煤3吨，节约了百分之几？(p*I,H:n(a5~2z2y
算式：提示.y)G)y0H9w.R5S(p*I,H:n(a5~2z2y
答：节约了百分之2K;H4K(~9A6q/k:M*n。(p*I,H:n(a5~2z2y