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Finding the Fourth Proportional to 85.96, 128.79 and 72.90

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Solution

The fourth proportional to 85.96, 128.79 and 72.90 is: 109.22

Step by Step Solution

  1. Step 1: Write the proportion equation
    85.96 : 128.79 = 72.90 : x
  2. Step 2: Convert to fraction form
    85.96/128.79 = 72.90/x
  3. Step 3: Cross multiply
    85.96x = 128.79 × 72.90
  4. Step 4: Simplify right side
    85.96x = 9,388.79
  5. Step 5: Solve for x
    x = 9,388.79/85.96
  6. Step 6: Final answer
    x = 109.22

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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.