3.小亮家新房屋装修,购进了同为50×50cm规格但品牌不同的两种瓷砖,他从这两种瓷砖(都是正方形)中各随机抽取五块测量,并将这十块瓷砖的边长(单位:cm)记录下表中:
算得两种品牌瓷砖边长的平均数相等,则从边长上可确定更标准的品牌为A.
| A种品牌 | 50.1 | 49.9 | 50.2 | 49.8 | 50.0 |
| B种品牌 | 50.3 | 49.6 | 50.0 | 50.4 | 49.7 |
2.
如图,在矩形ABCD中,AB=4,BC=5,点E、F、G、H分别在已知矩形的四条边上,且四边形EFGH也是矩形,GF=2EF.若设AE=a,AF=b,则a与b满足的关系为( )
| A. | $\left\{\begin{array}{l}{a+b=4}\\{a+2b=5}\end{array}\right.$ | B. | $\left\{\begin{array}{l}{2a+b=4}\\{a+2b=5}\end{array}\right.$ | C. | $\left\{\begin{array}{l}{a=2b}\\{2a+b=5}\end{array}\right.$ | D. | $\left\{\begin{array}{l}{2a+b=5}\\{a+2b=4}\end{array}\right.$ |
1.
如图是由一个圆柱和长方体组合而成的几何体,它的俯视图是( )
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| A. | B. | C. | D. |