Question

figures
count the number of cubes used to build each three - dimensional figure.
1
2
3
unit cubes
unit cubes
unit cubes
4
5
6
unit cubes
unit cubes
unit cubes
compare the number of unit cubes in each three - dimensional figure.

Explanation:

Step1: For figure 1

Count rows and columns. There are 5 rows and 4 columns of cubes on the top - layer. So the number of cubes is \(5\times4 = 20\).

Step2: For figure 2

There are 4 rows and 5 columns of cubes on the top - layer. The number of cubes is \(4\times5=20\).

Step3: For figure 3

There are 3 rows and 3 columns of cubes on the top - layer and 2 layers. The number of cubes is \(3\times3\times2 = 18\).

Step4: For figure 4

Count visible and hidden cubes. There are 3 cubes in the bottom - layer on the left and 6 cubes in the upper - layer. So the total number of cubes is \(3 + 6=9\).

Step5: For figure 5

There are 4 cubes in the bottom - layer, 4 cubes in the middle - layer and 2 cubes in the top - layer. The total number of cubes is \(4 + 4+2 = 10\).

Step6: For figure 6

There are 4 cubes in the bottom - layer and 1 cube on the top. The total number of cubes is \(4 + 1=5\).

Answer:

1. 20
2. 20
3. 18
4. 9
5. 10
6. 5