Mobile operator 2

A mobile operator compiled statistics on the average monthly number of received calls to the customer line. In 2010 it was 6000 calls, which were billed altogether at 360€. Fill in the table, if you know that the price per 1 call was always the same.

Year	2010	2011	2012	2013	2014	2015
average monthly number of received calls	6000	4000	3500	3000	2000	1500

What is the total billed amount in euros?

Final Answer:

z₁ =  240 Eur
z₂ =  210 Eur
z₃ =  180 Eur
z₄ =  120 Eur
z₅ =  90 Eur
s =  1200 Eur

Step-by-step explanation:

$$\begin{gathered} h_0=6000 \\ {h}_1=4000 \\ {h}_2=3500 \\ {h}_3=3000 \\ {h}_4=2000 \\ {h}_5=1500 \\ {z}_0=360\text{Eur} \\ c=z_0/h_0=360/6000=\frac{3}{50}=0.06\text{Eur/h} \\ {z}_1=c\cdot h_1=0.06\cdot 4000=240\text{Eur} \end{gathered}$$

$z_2=c\cdot h_2=0.06\cdot 3500=210\text{Eur}$

$z_3=c\cdot h_3=0.06\cdot 3000=180\text{Eur}$

$z_4=c\cdot h_4=0.06\cdot 2000=120\text{Eur}$

$z_5=c\cdot h_5=0.06\cdot 1500=90\text{Eur}$

$s=z_0+z_1+z_2+z_3+z_4+z_5=360+240+210+180+120+90=1200\text{Eur}$

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