6.“六•一”儿童节前夕,某超市用3000元购进A、B两种童装共120件,其中A种童装每件24元,B种童装每件30元.若设购买A种童装x件,B种童装y件,依题意列方程组正确的是( )
| A. | $\left\{\begin{array}{l}{x+y=120}\\{24x+30y=3000}\end{array}\right.$ | B. | $\left\{\begin{array}{l}{x+y=120}\\{30x+24y=300}\end{array}\right.$ | ||
| C. | $\left\{\begin{array}{l}{30x+24y=120}\\{x+y=3000}\end{array}\right.$ | D. | $\left\{\begin{array}{l}{24x+30y=120}\\{x+y=3000}\end{array}\right.$ |
4.下列命题中,是假命题的是( )
| A. | 等角的余角相等 | B. | 若a>b,且m≠0,则am>bm | ||
| C. | 三角形的外角和等于360° | D. | 两直线平行,同位角相等 |
2.下列计算中,不正确的是( )
0 284880 284888 284894 284898 284904 284906 284910 284916 284918 284924 284930 284934 284936 284940 284946 284948 284954 284958 284960 284964 284966 284970 284972 284974 284975 284976 284978 284979 284980 284982 284984 284988 284990 284994 284996 285000 285006 285008 285014 285018 285020 285024 285030 285036 285038 285044 285048 285050 285056 285060 285066 285074 366461
| A. | -2x+3x=x | B. | 2xy2•(-x)=-2x2y2 | C. | (-2x2y)3=-6x2y3 | D. | 6xy2÷2xy=3y |