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Finding the Fourth Proportional to 261.20, 391.74 and 78.56

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Solution

The fourth proportional to 261.20, 391.74 and 78.56 is: 117.82

Step by Step Solution

  1. Step 1: Write the proportion equation
    261.20 : 391.74 = 78.56 : x
  2. Step 2: Convert to fraction form
    261.20/391.74 = 78.56/x
  3. Step 3: Cross multiply
    261.20x = 391.74 × 78.56
  4. Step 4: Simplify right side
    261.20x = 30,775.09
  5. Step 5: Solve for x
    x = 30,775.09/261.20
  6. Step 6: Final answer
    x = 117.82

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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.