Beautiful garden

If 10 mm of water fell on a trapezoid-shaped garden with bases of 30 m and 20 m and a height of 20 m, how many buckets of water would we need to water the garden equally abundantly if the bucket had a volume of 15 l?

Correct answer:

n =  333

Step-by-step explanation:

$$\begin{gathered} a=30\text{m} \\ c=20\text{m} \\ h=20\text{m} \\ d=10\text{mm}\to \text{m}=10:1000\text{m}=0.01\text{m} \\ {S}_1=\frac{a+c}{2}\cdot h=\frac{30+20}{2}\cdot 20=500{\text{m}}^2 \\ V=S_1\cdot d=500\cdot 0.01=5{\text{m}}^3 \\ {V}_1=15\text{l} \\ {V}_2=V\to \text{l}=V\cdot 1000\text{l}=5\cdot 1000\text{l}=5000\text{l} \\ n=V_2/V_1=5000/15=333 \end{gathered}$$

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