Natalie is shopping at a used book and music store. A sign advertise 4 cds for $12. What is the unit rate for the cost of 1 cd?
2 answers:
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Answer:
<em><u>A.10000</u></em>
<em><u>B.25 more trees must be planted</u></em>
Step-by-step explanation:
⇒Given:
- The intial average yield per acre
= 150
- The initial number of trees per acre
= 100
- For each additional tree over 100, the average yield per tree decreases by 1 i.e , if the number trees become 101 , the avg yield becomes 149.
- Total yield = (number of trees per acre)
(average yield per acre)
<em>A.</em>
⇒If the total trees per acre is doubled , which means :
total number of trees per acre =
= 200
the yield will decrease by : -
⇒total yield =
<em>B.</em>
⇒to maximize the yield ,
let's take the number of trees per acre to be 100+y ;
and thus the average yield per acre = 150 - y;
total yield =
this is a quadratic equation. this can be rewritten as ,
⇒
In this equation , the total yield becomes maximum when y=25;
<u><em>⇒Thus the total number of trees per acre = 100+25 =125;</em></u>