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Finding the Fourth Proportional to 261.15, 391.79 and 139.40

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Solution

The fourth proportional to 261.15, 391.79 and 139.40 is: 209.13

Step by Step Solution

  1. Step 1: Write the proportion equation
    261.15 : 391.79 = 139.40 : x
  2. Step 2: Convert to fraction form
    261.15/391.79 = 139.40/x
  3. Step 3: Cross multiply
    261.15x = 391.79 × 139.40
  4. Step 4: Simplify right side
    261.15x = 54,615.53
  5. Step 5: Solve for x
    x = 54,615.53/261.15
  6. Step 6: Final answer
    x = 209.13

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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.