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Finding the Fourth Proportional to 261.30, 391.80 and 78.68

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Solution

The fourth proportional to 261.30, 391.80 and 78.68 is: 117.97

Step by Step Solution

  1. Step 1: Write the proportion equation
    261.30 : 391.80 = 78.68 : x
  2. Step 2: Convert to fraction form
    261.30/391.80 = 78.68/x
  3. Step 3: Cross multiply
    261.30x = 391.80 × 78.68
  4. Step 4: Simplify right side
    261.30x = 30,824.87
  5. Step 5: Solve for x
    x = 30,824.87/261.30
  6. Step 6: Final answer
    x = 117.97

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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.