Cooperatives - table

There are 3 cooperatives and privately owned farmers in the district. The table shows the wheat yields per hectare in t/ha and their areas in hectares in 4 entities. What was the average wheat yield in the district?

subject	yield [t/ha]	area [ha]
ZD1	4.9	640
ZD2	5.2	560
ZD3	4.8	1100
private	5.4	400

Correct answer:

a =  4.9956 t/ha

Step-by-step explanation:

$$\begin{gathered} S_1=640\text{ha} \\ {S}_2=560\text{ha} \\ {S}_3=1100\text{ha} \\ {S}_4=400\text{ha} \\ m=4.9\cdot S_1+5.2\cdot S_2+4.8\cdot S_3+5.4\cdot S_4=4.9\cdot 640+5.2\cdot 560+4.8\cdot 1100+5.4\cdot 400=13488\text{t} \\ a=\frac{m}{S_1+S_2+S_3+S_4}=\frac{13488}{640+560+1100+400}=4.9956\text{t/ha} \end{gathered}$$

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