[tex]4m = 40dm \\ 30m = 300dm \\ 10m = 100dm \\ 1m = 10dm[/tex]
[tex]V = \frac{(40 + 10) \times 300}{2} \times 10 = \frac{50 \times 300}{2} \times 10 = \frac{15000}{2} \times 10 = 15000 \times 5 = 75000 {dm}^{3} = \boxed{ 75.000l}[/tex]
