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Finding the Third Proportional to 428.50 and 689.75

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Solution

The third proportional to 428.50 and 689.75 is: 1,110.28

Step by Step Solution

  1. Step 1: Write the proportion equation
    428.50 : 689.75 = 689.75 : x
  2. Step 2: Convert to fraction form
    428.50/689.75 = 689.75/x
  3. Step 3: Cross multiply
    428.50x = 689.75 × 689.75
  4. Step 4: Simplify right side
    428.50x = 475,755.06
  5. Step 5: Solve for x
    x = 475,755.06/428.50
  6. Step 6: Final answer
    x = 1,110.28

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Why These Related Problems?

These problems maintain the same ratio (1.61) or explore similar proportional relationships. Practicing with related ratios helps build understanding of proportional relationships.