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Finding the Fourth Proportional to 261.07, 391.49 and 78.42

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Solution

The fourth proportional to 261.07, 391.49 and 78.42 is: 117.60

Step by Step Solution

  1. Step 1: Write the proportion equation
    261.07 : 391.49 = 78.42 : x
  2. Step 2: Convert to fraction form
    261.07/391.49 = 78.42/x
  3. Step 3: Cross multiply
    261.07x = 391.49 × 78.42
  4. Step 4: Simplify right side
    261.07x = 30,700.65
  5. Step 5: Solve for x
    x = 30,700.65/261.07
  6. Step 6: Final answer
    x = 117.60

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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.