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Finding the Third Proportional to 689 and 978.50

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Solution

The third proportional to 689 and 978.50 is: 1,389.64

Step by Step Solution

  1. Step 1: Write the proportion equation
    689 : 978.50 = 978.50 : x
  2. Step 2: Convert to fraction form
    689/978.50 = 978.50/x
  3. Step 3: Cross multiply
    689x = 978.50 × 978.50
  4. Step 4: Simplify right side
    689x = 957,462.25
  5. Step 5: Solve for x
    x = 957,462.25/689
  6. Step 6: Final answer
    x = 1,389.64

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These problems maintain the same ratio (1.42) or explore similar proportional relationships. Practicing with related ratios helps build understanding of proportional relationships.