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Finding the Fourth Proportional to 256.78, 385.13 and 74.20

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Solution

The fourth proportional to 256.78, 385.13 and 74.20 is: 111.29

Step by Step Solution

  1. Step 1: Write the proportion equation
    256.78 : 385.13 = 74.20 : x
  2. Step 2: Convert to fraction form
    256.78/385.13 = 74.20/x
  3. Step 3: Cross multiply
    256.78x = 385.13 × 74.20
  4. Step 4: Simplify right side
    256.78x = 28,576.28
  5. Step 5: Solve for x
    x = 28,576.28/256.78
  6. Step 6: Final answer
    x = 111.29

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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.