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3 years ago

The time it takes you to go a certain distance varies inversely with the speed of travel. Suppose it takes you 4 hours to get to

a sports event driving at a rate of 50 miles per hour.
a) Find the constant of variation. Write the particular equation expressing time in terms of speed.

b) How long will it take you to get to the event if you drive at 40 mph?

Mathematics

1 answer:

fgiga [73]3 years ago

3 0

$\bf \qquad \qquad \textit{inverse proportional variation}
\\\\
\textit{\underline{y} varies inversely with \underline{x}}\qquad \qquad y=\cfrac{k}{x}\impliedby 
\begin{array}{llll}
k=constant\ of\\
\qquad variation
\end{array}\\\\
-------------------------------$

$\bf \textit{time it takes varies inversely with the speed rate}\qquad \stackrel{time}{t}=\cfrac{k}{\stackrel{rate}{r}}
\\\\\\
\textit{we also know that }
\begin{cases}
t=\stackrel{hrs}{4}\\
r=\stackrel{mph}{50}
\end{cases}\implies 4=\cfrac{k}{50}\implies 200=k
\\\\\\
\boxed{t=\cfrac{200}{r}}
\\\\\\
\textit{if your rate r = 40, what is your distance \underline{t}?}\qquad t=\cfrac{200}{40}$

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1) Point $(1,0)$ -----> see the attached figure N $1$

2) The value of x is $4$

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4) $(1,1)$

5) $y>-5x+3$

Step-by-step explanation:

Part 1)

we know that

If the point satisfy the inequality

then

the point must be included in the shaded area

The point $(1,0)$ is included in the shaded area

Part 2)

we have

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see the attached figure N $2$

we know that

The value for x on the boundary line and the x axis is equal to the x-intercept of the line $x-2y= 4$

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The solution is $x=4$

Part 3)

we have

$x\geq 0$ -----> inequality A

The solution of the inequality A is in the first and fourth quadrant

$y\geq 0$ -----> inequality B

The solution of the inequality B is in the first and second quadrant

the solution of the inequality A and the inequality B is the first quadrant

Part 4) Which ordered pair is a solution of the inequality?

we have

$y\geq 4x-5$

we know that

If a ordered pair is a solution of the inequality

then

the ordered pair must be satisfy the inequality

we're going to verify all the cases

case A) point $(3,4)$

Substitute the value of x and y in the inequality

$x=3,y=4$

$4\geq 4(3)-5$

$4\geq 7$ ------> is not true

therefore

the point $(3,4)$ is not a solution of the inequality

case B) point $(2,1)$

Substitute the value of x and y in the inequality

$x=2,y=1$

$1\geq 4(2)-5$

$1\geq 3$ ------> is not true

therefore

the point $(2,1)$ is not a solution of the inequality

case C) point $(3,0)$

Substitute the value of x and y in the inequality

$x=3,y=0$

$0\geq 4(3)-5$

$0\geq 7$ ------> is not true

therefore

the point $(3,0)$ is not a solution of the inequality

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Substitute the value of x and y in the inequality

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therefore

the point $(1,1)$ is a solution of the inequality

Part 5) Write an inequality to match the graph

we know that

The equation of the line has a negative slope

The y-intercept is the point $(3,0)$

The x-intercept is a positive number

The solution is the shaded area above the dashed line

the equation of the line is $y=-5x+3$

The inequality is $y>-5x+3$

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