7.
如图,矩形ABCD的周长是20cm,以AB,AD为边向外作正方形ABEF和正方形ADGH,若正方形ABEF和ADGH的面积之和为68cm2,那么矩形ABCD的面积是( )
| A. | 9cm2 | B. | 16cm2 | C. | 21cm2 | D. | 24cm2 |
6.
如图所示电路,任意闭合两个开关,能使灯L2亮起来的概率是( )
0 293842 293850 293856 293860 293866 293868 293872 293878 293880 293886 293892 293896 293898 293902 293908 293910 293916 293920 293922 293926 293928 293932 293934 293936 293937 293938 293940 293941 293942 293944 293946 293950 293952 293956 293958 293962 293968 293970 293976 293980 293982 293986 293992 293998 294000 294006 294010 294012 294018 294022 294028 294036 366461
| A. | $\frac{1}{2}$ | B. | $\frac{1}{3}$ | C. | $\frac{2}{3}$ | D. | $\frac{1}{5}$ |