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将棱长相等的正方体按图所示的形状摆放,从上往下依次为第1层,第2层,…,则第20...
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将棱长相等的正方体按图所示的形状摆放,从上往下依次为第1层,第2层,…,则第20层正方体的个数是( )
A.420
B.440
C.210
D.220
考点分析:
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