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Finding the Fourth Proportional to 87.20, 128.28 and 87.20

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Solution

The fourth proportional to 87.20, 128.28 and 87.20 is: 128.28

Step by Step Solution

  1. Step 1: Write the proportion equation
    87.20 : 128.28 = 87.20 : x
  2. Step 2: Convert to fraction form
    87.20/128.28 = 87.20/x
  3. Step 3: Cross multiply
    87.20x = 128.28 × 87.20
  4. Step 4: Simplify right side
    87.20x = 11,186.02
  5. Step 5: Solve for x
    x = 11,186.02/87.20
  6. Step 6: Final answer
    x = 128.28

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Why These Related Problems?

These problems maintain the same ratio (1.47) or explore similar proportional relationships. Practicing with related ratios helps build understanding of proportional relationships.