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Finding the Fourth Proportional to 261.40, 391.95 and 78.76

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Solution

The fourth proportional to 261.40, 391.95 and 78.76 is: 118.09

Step by Step Solution

  1. Step 1: Write the proportion equation
    261.40 : 391.95 = 78.76 : x
  2. Step 2: Convert to fraction form
    261.40/391.95 = 78.76/x
  3. Step 3: Cross multiply
    261.40x = 391.95 × 78.76
  4. Step 4: Simplify right side
    261.40x = 30,869.98
  5. Step 5: Solve for x
    x = 30,869.98/261.40
  6. Step 6: Final answer
    x = 118.09

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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.