Algebra II : Indirect Proportionality

Study concepts, example questions & explanations for Algebra II

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Example Questions

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Example Question #21 : Indirect Proportionality

x varies inversely with y. When x=10, y=6. When x=3, what is y?

Possible Answers:

Correct answer:

Explanation:

Inverse variation takes the form:

Plugging in:

Then solve when x=3:

Example Question #22 : Indirect Proportionality

The rate of speed is indirectly proportional to the time it takes to travel somewhere. If a person walks at a rate of 3 miles per hour and it takes them 4 hours to get to their destination how far did they travel?

Possible Answers:

Correct answer:

Explanation:

For an indirect proportionality, use the equation

If rate of speed is indirectly proportional to the time, then the speed is y (3 miles per hour) and the time is x (4 hours).

Replace those into the indirect proportionality formula

Solve for k by multiplying by 4 on both sides

The person traveled 12 miles.

Example Question #23 : Indirect Proportionality

A turtle moves at a pace that is inversely proportional to its weight. Suppose at five pounds it moves two feet per minute. What would be the turtle's speed in feet per minute if it weighed eight pounds?

Possible Answers:

Correct answer:

Explanation:

Write the relationship for inverse proportionality.  If one variable increases, the other variable must decrease.

  or  

Let  be the turtle's speed, and  is the weight of the turtle since the turtle's speed depends on its weight.

Solve for  by substituting the initial conditions.

Multiply by two on both sides.

Substitute this value back into the original equation.

The relationship is:  

Substitute eight pounds to find its speed.

The turtle will move at a rate of  feet per minute.

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