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Finding the Fourth Proportional to 1,405.78, 2,108.64 and 431.86

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Solution

The fourth proportional to 1,405.78, 2,108.64 and 431.86 is: 647.78

Step by Step Solution

  1. Step 1: Write the proportion equation
    1,405.78 : 2,108.64 = 431.86 : x
  2. Step 2: Convert to fraction form
    1,405.78/2,108.64 = 431.86/x
  3. Step 3: Cross multiply
    1,405.78x = 2,108.64 × 431.86
  4. Step 4: Simplify right side
    1,405.78x = 910,626.73
  5. Step 5: Solve for x
    x = 910,626.73/1,405.78
  6. Step 6: Final answer
    x = 647.78

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Why These Related Problems?

These problems maintain the same ratio (1.50) or explore similar proportional relationships. Practicing with related ratios helps build understanding of proportional relationships.