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Finding the Fourth Proportional to 261, 391.58 and 78.39

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Solution

The fourth proportional to 261, 391.58 and 78.39 is: 117.61

Step by Step Solution

  1. Step 1: Write the proportion equation
    261 : 391.58 = 78.39 : x
  2. Step 2: Convert to fraction form
    261/391.58 = 78.39/x
  3. Step 3: Cross multiply
    261x = 391.58 × 78.39
  4. Step 4: Simplify right side
    261x = 30,696.15
  5. Step 5: Solve for x
    x = 30,696.15/261
  6. Step 6: Final answer
    x = 117.61

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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.