4.甲乙两人在跳远练习中,6次成绩分别为(单位:米):
甲:3.8 3.8 3.9 3.9 4 4;
乙:3.8 3.9 3.9 3.9 3.9 4.
则这次跳远练习中,甲乙两人成绩方差的大小关系是( )
甲:3.8 3.8 3.9 3.9 4 4;
乙:3.8 3.9 3.9 3.9 3.9 4.
则这次跳远练习中,甲乙两人成绩方差的大小关系是( )
| A. | s2甲>s2乙 | B. | s2甲<s2乙 | C. | s2甲=s2乙 | D. | 无法确定 |
17.小强到体育用品商店购买羽毛球球拍和乒乓球球拍,已知购买1副羽毛球球拍和1副乒乓球球拍共需50元,小强一共用320元购买了6副同样的羽毛球拍和10副同样的乒乓球拍.若设每副羽毛球拍为x元,每副乒乓球拍为y元,根据题意,下面所列方程组正确的是( )
| A. | $\left\{\begin{array}{l}{x+y=50}\\{10(x+y)=320}\end{array}\right.$ | B. | $\left\{\begin{array}{l}{x+y=50}\\{6x+10y=320}\end{array}\right.$ | ||
| C. | $\left\{\begin{array}{l}{x+y=50}\\{6x+y=320}\end{array}\right.$ | D. | $\left\{\begin{array}{l}{x+y=50}\\{10x+6y=320}\end{array}\right.$ |
16.
如图,点E在AB的延长线上,下列条件中能判断AD∥BC的是( )
0 284770 284778 284784 284788 284794 284796 284800 284806 284808 284814 284820 284824 284826 284830 284836 284838 284844 284848 284850 284854 284856 284860 284862 284864 284865 284866 284868 284869 284870 284872 284874 284878 284880 284884 284886 284890 284896 284898 284904 284908 284910 284914 284920 284926 284928 284934 284938 284940 284946 284950 284956 284964 366461
| A. | ∠1=∠2 | B. | ∠3=∠4 | C. | ∠C=∠CBE | D. | ∠C+∠ABC=180° |