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Finding the Fourth Proportional to 85.90, 128.52 and 80.86

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Solution

The fourth proportional to 85.90, 128.52 and 80.86 is: 120.98

Step by Step Solution

  1. Step 1: Write the proportion equation
    85.90 : 128.52 = 80.86 : x
  2. Step 2: Convert to fraction form
    85.90/128.52 = 80.86/x
  3. Step 3: Cross multiply
    85.90x = 128.52 × 80.86
  4. Step 4: Simplify right side
    85.90x = 10,392.13
  5. Step 5: Solve for x
    x = 10,392.13/85.90
  6. Step 6: Final answer
    x = 120.98

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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.