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Finding the Fourth Proportional to 261.28, 391.97 and 78.69

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Solution

The fourth proportional to 261.28, 391.97 and 78.69 is: 118.05

Step by Step Solution

  1. Step 1: Write the proportion equation
    261.28 : 391.97 = 78.69 : x
  2. Step 2: Convert to fraction form
    261.28/391.97 = 78.69/x
  3. Step 3: Cross multiply
    261.28x = 391.97 × 78.69
  4. Step 4: Simplify right side
    261.28x = 30,844.12
  5. Step 5: Solve for x
    x = 30,844.12/261.28
  6. Step 6: Final answer
    x = 118.05

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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.