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Finding the Fourth Proportional to 645.21, 890.39 and 505.47

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Solution

The fourth proportional to 645.21, 890.39 and 505.47 is: 697.54

Step by Step Solution

  1. Step 1: Write the proportion equation
    645.21 : 890.39 = 505.47 : x
  2. Step 2: Convert to fraction form
    645.21/890.39 = 505.47/x
  3. Step 3: Cross multiply
    645.21x = 890.39 × 505.47
  4. Step 4: Simplify right side
    645.21x = 450,062.91
  5. Step 5: Solve for x
    x = 450,062.91/645.21
  6. Step 6: Final answer
    x = 697.54

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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.