Lawns

Before a sports hall are two equally large rectangular lawns measuring 40 m and 12 m. Maintenance of a 10m² lawn costs 45 CZK yearly. On each lawn is a circular flowerbed with a diameter of 8 meters. How much money is needed each year to take on lawn care? Result round to the nearest CZK crown.

Correct answer:

x =  3868 Kc

Step-by-step explanation:

$$\begin{gathered} a=40\text{m} \\ b=12\text{m} \\ n=2 \\ c=45/10=\frac{9}{2}=4.5{\text{Kc/m}}^2 \\ D=8\text{m} \\ r=D/2=8/2=4\text{m} \\ S=a\cdot b-\pi \cdot r^2=40\cdot 12-3.1416\cdot 4^2\doteq 429.7345{\text{m}}^2 \\ x=n\cdot c\cdot S=2\cdot 4.5\cdot 429.7345=3868\text{Kc} \end{gathered}$$

Try another example