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Finding the Fourth Proportional to 102.15, 140.86 and 78.84

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Solution

The fourth proportional to 102.15, 140.86 and 78.84 is: 108.72

Step by Step Solution

  1. Step 1: Write the proportion equation
    102.15 : 140.86 = 78.84 : x
  2. Step 2: Convert to fraction form
    102.15/140.86 = 78.84/x
  3. Step 3: Cross multiply
    102.15x = 140.86 × 78.84
  4. Step 4: Simplify right side
    102.15x = 11,105.40
  5. Step 5: Solve for x
    x = 11,105.40/102.15
  6. Step 6: Final answer
    x = 108.72

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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.