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Finding the Fourth Proportional to 781.25, 1,078.31 and 486.61

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Solution

The fourth proportional to 781.25, 1,078.31 and 486.61 is: 671.64

Step by Step Solution

  1. Step 1: Write the proportion equation
    781.25 : 1,078.31 = 486.61 : x
  2. Step 2: Convert to fraction form
    781.25/1,078.31 = 486.61/x
  3. Step 3: Cross multiply
    781.25x = 1,078.31 × 486.61
  4. Step 4: Simplify right side
    781.25x = 524,714.95
  5. Step 5: Solve for x
    x = 524,714.95/781.25
  6. Step 6: Final answer
    x = 671.64

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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.