Exam 10: Mathematical Modeling and Variation

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State sales tax is based on retail price.An item that sells for $180.99 has a sales tax of $17.4.Find a mathematical model that gives the amount of sales tax y in terms of the retail price x.Use the model to find the sales tax on a $589.99 purchase.(Round your answer to four decimal places. ) ​

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An overhead garage door has two springs,one on each side of the door (see figure).A force of 2020 pounds is required to stretch each spring 1 foot.Because of a pulley system,the springs stretch only one-half the distance the door travels.The door moves a total of x=18x = 18 feet,and the springs are at their natural length when the door is open.Find the combined lifting force applied to the door by the springs when the door is closed.​  An overhead garage door has two springs,one on each side of the door (see figure).A force of  20  pounds is required to stretch each spring 1 foot.Because of a pulley system,the springs stretch only one-half the distance the door travels.The door moves a total of  x = 18  feet,and the springs are at their natural length when the door is open.Find the combined lifting force applied to the door by the springs when the door is closed.​   ​

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Use the given value of k to complete the table for the direct variation model​ y=kx2y = k x ^ { 2 } . ​ Plot the points on a rectangular coordinate system. x 8 10 12 14 16 y=k k=

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Use the given value of k to complete the table for the inverse variation model​ y=kx2y = \frac { k } { x ^ { 2 } } Plot the points on a rectangular coordinate system. x 8 10 12 14 16 y= k=5

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On a yardstick with scales in inches and centimeters,you notice that 11 inches is approximately the same length as 33 centimeters.Use this information to find a mathematical model that relates centimeters y to inches x.Then use the model to find the numbers of centimeters in 60 inches and 70 inches.(Round your answer to one decimal place. ) ​

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Assume that y is directly proportional to x.Use the given x-value and y-value to find a linear model that relates y and x.​ x=38,y=2400x = 38 , y = 2400 ​ ​

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Determine whether the variation model below is of the form y=kxy = k x or y=kxy = \frac { k } { x } . x 12 24 36 48 60 Y 118\frac { 1 } { 18 }136\frac { 1 } { 36 }154\frac { 1 } { 54 }172\frac { 1 } { 72 }190\frac { 1 } { 90 }

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Find a mathematical model representing the statement.(Determine the constant of proportionality. ) ​ F is jointly proportional to r and the third power of s. (F=24750 when r=18 and s=5.)( F = 24750 \text { when } r = 18 \text { and } s = 5 . )

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Determine whether the variation model is of the form y=kxy = k x or y=kxy = \frac { k } { x } and find k.Then write a model that relates y and x. x 5 10 15 20 25 y -1.5 -3 -4.5 -6 -7.5

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Determine whether the variation model below is of the form y=kxy = k x or y=kxy = \frac { k } { x } . x 13 26 39 52 65 Y 3 6 9 12 15

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Find a mathematical model for the verbal statement: "m varies directly as the square of w and inversely as s."

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Find a mathematical model representing the statement.(Determine the constant of proportionality. ) ​ Y varies inversely as x. (y=9 when x=45.)( y = 9 \text { when } x = 45 . )

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Assume that y is directly proportional to x.Use the given x-value and y-value to find a linear model that relates y and x.​ x=5,y=380x = 5 , y = 380

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The coiled spring of a toy supports the weight of a child.The spring is compressed a distance of 1.6 inches by the weight of a 35-pound child.The toy will not work properly if its spring is compressed more than 6 inches.What is the weight of the heaviest child who should be allowed to use the toy? (Round your answer to two decimal places. ) ​

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Use the given value of k to complete the table for the inverse variation model​ y=kx2y = \frac { k } { x ^ { 2 } } Plot the points on a rectangular coordinate system. x 8 10 12 14 16 y= k=10k = 10 Use the given value of k to complete the table for the inverse variation model​  y = \frac { k } { x ^ { 2 } }  Plot the points on a rectangular coordinate system.   \begin{array} { | c | c | c | c | c | c | }  \hline x & 8 & 10 & 12 & 14 & 16 \\ \hline y = \frac { k } { x ^ { 2 } } & & & & & \\ \hline \end{array}   k = 10  ​

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When buying gasoline,you notice that 16 gallons of gasoline is approximately the same amount of gasoline as 51 liters.Use this information to find a linear model that relates liters y to gallons x.Then use the model to find the numbers of liters in 25 gallons and 45 gallons. (Round your answer to one decimal place. ) ​

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The sales tax on an item with a retail price of $972 is $68.04.Create a variational model that gives the retail price,y,in terms of the sales tax,x,and use it to determine the retail price of an item that has a sales tax of $82.62.

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Use the fact that the diameter of the largest particle that can be moved by a stream varies approximately directly as the square of the velocity of the stream. ​ A stream with a velocity of 15\frac { 1 } { 5 } mile per hour can move coarse sand particles about 0.07 inch in diameter.Approximate the velocity required to carry particles 0.2 inch in diameter.(Round your answer to two decimal places. ) ​

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Find a mathematical model for the verbal statement: ​ "Q is jointly proportional to the cube of h and the square root of m." ​

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Use the given value of k to complete the table for the direct variation model​ y=kx2y = k x ^ { 2 } . ​ Plot the points on a rectangular coordinate system. x 8 10 12 14 16 y=k k=

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