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Finding the Fourth Proportional to 428.38, 642.16 and 390.34

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Solution

The fourth proportional to 428.38, 642.16 and 390.34 is: 585.14

Step by Step Solution

  1. Step 1: Write the proportion equation
    428.38 : 642.16 = 390.34 : x
  2. Step 2: Convert to fraction form
    428.38/642.16 = 390.34/x
  3. Step 3: Cross multiply
    428.38x = 642.16 × 390.34
  4. Step 4: Simplify right side
    428.38x = 250,662.03
  5. Step 5: Solve for x
    x = 250,662.03/428.38
  6. Step 6: Final answer
    x = 585.14

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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.