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Finding the Fourth Proportional to 1,217, 1,679.46 and 665

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Solution

The fourth proportional to 1,217, 1,679.46 and 665 is: 917.70

Step by Step Solution

  1. Step 1: Write the proportion equation
    1,217 : 1,679.46 = 665 : x
  2. Step 2: Convert to fraction form
    1,217/1,679.46 = 665/x
  3. Step 3: Cross multiply
    1,217x = 1,679.46 × 665
  4. Step 4: Simplify right side
    1,217x = 1,116,840.90
  5. Step 5: Solve for x
    x = 1,116,840.90/1,217
  6. Step 6: Final answer
    x = 917.70

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Why These Related Problems?

These problems maintain the same ratio (1.38) or explore similar proportional relationships. Practicing with related ratios helps build understanding of proportional relationships.