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Finding the Fourth Proportional to 261.18, 391.65 and 78.54

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Solution

The fourth proportional to 261.18, 391.65 and 78.54 is: 117.77

Step by Step Solution

  1. Step 1: Write the proportion equation
    261.18 : 391.65 = 78.54 : x
  2. Step 2: Convert to fraction form
    261.18/391.65 = 78.54/x
  3. Step 3: Cross multiply
    261.18x = 391.65 × 78.54
  4. Step 4: Simplify right side
    261.18x = 30,758.72
  5. Step 5: Solve for x
    x = 30,758.72/261.18
  6. Step 6: Final answer
    x = 117.77

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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.