一个实心积木的外表面全部涂上油漆,然后切成若干个 22-cm 的小正方体,如图所示。 (a) 书秀(Shu Xiu)从该积木中切出了多少个 22-cm 的正方体? (b) 在这些 22-cm 的正方体中,有多少个正方体没有任何一个面被涂上油漆?

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完整解法

12

1. Find the number of $2$-cm cubes along each dimension of the block.

Number of cubes along length = 32÷2=1632 \div 2 = 16
Number of cubes along height = 24÷2=1224 \div 2 = 12
Number of cubes along depth = 12÷2=612 \div 2 = 6

2. Calculate the total number of cubes for part (a).

Total cubes = 16×12×6=115216 \times 12 \times 6 = 1152

3. Determine the dimensions of the unpainted interior region in terms of cubes.

The unpainted cubes form an inner block. We remove 11 layer of cubes from each of the 66 faces (i.e., 22 layers per dimension).
Interior length = 16−2=1416 - 2 = 14 cubes
Interior height = 12−2=1012 - 2 = 10 cubes
Interior depth = 6−2=46 - 2 = 4 cubes

4. Calculate the total number of unpainted cubes for part (b).

Number of unpainted cubes = 14×10×4=56014 \times 10 \times 4 = 560

答案

(a) 11521152
(b) 560560

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