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Finding the Fourth Proportional to 85.60, 128.64 and 68.64

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Solution

The fourth proportional to 85.60, 128.64 and 68.64 is: 103.15

Step by Step Solution

  1. Step 1: Write the proportion equation
    85.60 : 128.64 = 68.64 : x
  2. Step 2: Convert to fraction form
    85.60/128.64 = 68.64/x
  3. Step 3: Cross multiply
    85.60x = 128.64 × 68.64
  4. Step 4: Simplify right side
    85.60x = 8,829.85
  5. Step 5: Solve for x
    x = 8,829.85/85.60
  6. Step 6: Final answer
    x = 103.15

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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.