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Finding the Fourth Proportional to 261.15, 391.69 and 78.60

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Solution

The fourth proportional to 261.15, 391.69 and 78.60 is: 117.88

Step by Step Solution

  1. Step 1: Write the proportion equation
    261.15 : 391.69 = 78.60 : x
  2. Step 2: Convert to fraction form
    261.15/391.69 = 78.60/x
  3. Step 3: Cross multiply
    261.15x = 391.69 × 78.60
  4. Step 4: Simplify right side
    261.15x = 30,784.65
  5. Step 5: Solve for x
    x = 30,784.65/261.15
  6. Step 6: Final answer
    x = 117.88

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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.