下面的立体图形是由 1 厘米的正方体组成的。求该立体图形的体积。 答：___ $\text{cm}^3$

1. Count the number of cubes in each row from back to front

Back row: $4 + 3 + 2 + 1 = 10$ cubes
Second row: $3 + 2 + 1 = 6$ cubes
Third row: $2 + 1 = 3$ cubes
Front row: $1$ cube

2. Calculate the total number of cubes and the total volume

Total number of cubes = $10 + 6 + 3 + 1 = 20$
Since each cube has a volume of $1\text{ cm}^3$, total volume = $20 \times 1 = 20\text{ cm}^3$