Ulrich and Jacinta work for a cleaning business to earn college tuition money. Jacinta can clean a client's apartment in 1 hour 20 minutes if she works alone. Ulrich and Jacinta can
clean the apartment in 48 minutes if they work together. How long (in minutes) does it
take Ulrich to clean the apartment if he works alone? Assume both people work at steady
rates and their rates are not affected by either working alone or working togeth

20

step-by-step explanation:

answer: 204

step-by-step explanation:

we are told that the revenue is

x⋅(4080−10x)=−10x^2+4080x

this is a quadratic function, so to maximize it we should find the x-value of its vertex. recall that the x-value of the vertex of the parabola ax^2+bx+c is given by the formula −b/2a.

so in this case, we have a=−10 and b=4080, so the x-value of the vertex is

−b/2a= −(4080)/2(−10)=204

this is a direct variation proportion. y = kx

y is the total amount due, k is the constant of variation, and x is the number of texts sent.

plug in the 3.20 and the 16 to solve for the "k". this is the constant of proportionality. it is the value that will not change.

3.20 = k(16). solving you get $.20 per text.

the equation would then be y = .20x