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Finding the Fourth Proportional to 385.28, 578 and 128.76

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Solution

The fourth proportional to 385.28, 578 and 128.76 is: 193.17

Step by Step Solution

  1. Step 1: Write the proportion equation
    385.28 : 578 = 128.76 : x
  2. Step 2: Convert to fraction form
    385.28/578 = 128.76/x
  3. Step 3: Cross multiply
    385.28x = 578 × 128.76
  4. Step 4: Simplify right side
    385.28x = 74,423.28
  5. Step 5: Solve for x
    x = 74,423.28/385.28
  6. Step 6: Final answer
    x = 193.17

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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.