SOLUTION: Hello I need help setting up the equation for this word problem. The monthly revenue achieved by selling x wristwatches is x(40-o.2x)dollars. The cost of each watch is $28. How

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Question 473103: Hello I need help setting up the equation for this word problem.
The monthly revenue achieved by selling x wristwatches is x(40-o.2x)dollars. The cost of each watch is $28. Howw many watched must be sold each month to acheive a profit (revenue minus cost) of at leaast $100? Must set up an algebraic inequality and solve it.
Thank you!
Answer by ankor@dixie-net.com(22740) About Me  (Show Source):
You can put this solution on YOUR website!
The monthly revenue achieved by selling x wristwatches is x(40-0.2x)dollars.
The cost of each watch is $28.
How many watches must be sold each month to acheive a profit (revenue minus cost) of at leaast $100?
Must set up an algebraic inequality and solve it.
:
Cost = 28x
:
Rev - cost = at least $100
x(40-.2x) - 28x => 100
40x - .2x^2 - 28x => 100
-.2x^2 + 12x - 100 => 0
multiply by -5, to make easier to factor
x^2 - 60x + 500 => 0
factors to:
x = 50
x => 10
:
We can say at least sell 10 watches to make at least $100