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Finding the Fourth Proportional to 128.64, 192.88 and 77.28

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Solution

The fourth proportional to 128.64, 192.88 and 77.28 is: 115.87

Step by Step Solution

  1. Step 1: Write the proportion equation
    128.64 : 192.88 = 77.28 : x
  2. Step 2: Convert to fraction form
    128.64/192.88 = 77.28/x
  3. Step 3: Cross multiply
    128.64x = 192.88 × 77.28
  4. Step 4: Simplify right side
    128.64x = 14,905.77
  5. Step 5: Solve for x
    x = 14,905.77/128.64
  6. Step 6: Final answer
    x = 115.87

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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.