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Finding the Fourth Proportional to 108.78, 162.96 and 85.86

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Solution

The fourth proportional to 108.78, 162.96 and 85.86 is: 128.62

Step by Step Solution

  1. Step 1: Write the proportion equation
    108.78 : 162.96 = 85.86 : x
  2. Step 2: Convert to fraction form
    108.78/162.96 = 85.86/x
  3. Step 3: Cross multiply
    108.78x = 162.96 × 85.86
  4. Step 4: Simplify right side
    108.78x = 13,991.75
  5. Step 5: Solve for x
    x = 13,991.75/108.78
  6. Step 6: Final answer
    x = 128.62

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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.