# Algebra II : Direct Proportionality

## Example Questions

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### Example Question #21 : Basic Single Variable Algebra

Suppose a runner's distance is directly proportional to her time.  If the runner completes 6 miles in 70 minutes, how many minutes did it take the runner to run 4 miles?      Explanation:

Write the equation for direct proportionality. Substitute the distance and time to solve for the constant. Divide by 70 on both sides.  Substitute this value back to .

The equation becomes: Substitute to determine how long it took the runner to run 4 miles. Multiply by on both sides to isolate the time variable. Simplify both sides.

The answer is: ### Example Question #22 : Direct Proportionality

The distance of a cyclist is directly proportional to the time he has traveled. Suppose he has traveled 12 miles in 1.5 hours. How far does he travel in a half hour?      Explanation:

Write the equation for direct proportionality. Substitute the distance and time given to solve for the constant of proportionality, . Divide by 1.5 on both sides.  Write the equation. Substitute half an hour for the time to determine the distance the biker has traveled. The biker traveled four miles in a half hour.

The answer is: 1 3 Next →

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