A:at; for
B:in; to
C:at; with
把1999.728四舍五入,使其精确到十位,那么所得近似数的有效数字为( )
In Western countries , people usually do not open gifts right away.
若实数x,y满足不等式组 {x-y+5≥0x+y≥0x≤3则2x+4y的最小值是( )
口算我能行.
10×6=____
2×30=____
4×21=____
3×23=____