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Finding the Fourth Proportional to 78.86, 108.90 and 55.61

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Solution

The fourth proportional to 78.86, 108.90 and 55.61 is: 76.79

Step by Step Solution

  1. Step 1: Write the proportion equation
    78.86 : 108.90 = 55.61 : x
  2. Step 2: Convert to fraction form
    78.86/108.90 = 55.61/x
  3. Step 3: Cross multiply
    78.86x = 108.90 × 55.61
  4. Step 4: Simplify right side
    78.86x = 6,055.38
  5. Step 5: Solve for x
    x = 6,055.38/78.86
  6. Step 6: Final answer
    x = 76.79

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Why These Related Problems?

These problems maintain the same ratio (1.38) or explore similar proportional relationships. Practicing with related ratios helps build understanding of proportional relationships.