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Finding the Fourth Proportional to 85.67, 128.40 and 65.31

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Solution

The fourth proportional to 85.67, 128.40 and 65.31 is: 97.89

Step by Step Solution

  1. Step 1: Write the proportion equation
    85.67 : 128.40 = 65.31 : x
  2. Step 2: Convert to fraction form
    85.67/128.40 = 65.31/x
  3. Step 3: Cross multiply
    85.67x = 128.40 × 65.31
  4. Step 4: Simplify right side
    85.67x = 8,385.80
  5. Step 5: Solve for x
    x = 8,385.80/85.67
  6. Step 6: Final answer
    x = 97.89

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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.