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Finding the Fourth Proportional to 428.60, 642.56 and 387.08

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Solution

The fourth proportional to 428.60, 642.56 and 387.08 is: 580.31

Step by Step Solution

  1. Step 1: Write the proportion equation
    428.60 : 642.56 = 387.08 : x
  2. Step 2: Convert to fraction form
    428.60/642.56 = 387.08/x
  3. Step 3: Cross multiply
    428.60x = 642.56 × 387.08
  4. Step 4: Simplify right side
    428.60x = 248,722.12
  5. Step 5: Solve for x
    x = 248,722.12/428.60
  6. Step 6: Final answer
    x = 580.31

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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.