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Finding the Fourth Proportional to 261.18, 391.64 and 139.55

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Solution

The fourth proportional to 261.18, 391.64 and 139.55 is: 209.25

Step by Step Solution

  1. Step 1: Write the proportion equation
    261.18 : 391.64 = 139.55 : x
  2. Step 2: Convert to fraction form
    261.18/391.64 = 139.55/x
  3. Step 3: Cross multiply
    261.18x = 391.64 × 139.55
  4. Step 4: Simplify right side
    261.18x = 54,650.71
  5. Step 5: Solve for x
    x = 54,650.71/261.18
  6. Step 6: Final answer
    x = 209.25

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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.