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Finding the Fourth Proportional to 428.10, 640.55 and 389.70

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Solution

The fourth proportional to 428.10, 640.55 and 389.70 is: 583.09

Step by Step Solution

  1. Step 1: Write the proportion equation
    428.10 : 640.55 = 389.70 : x
  2. Step 2: Convert to fraction form
    428.10/640.55 = 389.70/x
  3. Step 3: Cross multiply
    428.10x = 640.55 × 389.70
  4. Step 4: Simplify right side
    428.10x = 249,622.34
  5. Step 5: Solve for x
    x = 249,622.34/428.10
  6. Step 6: Final answer
    x = 583.09

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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.