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Finding the Fourth Proportional to 428.70, 641.70 and 415.20

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Solution

The fourth proportional to 428.70, 641.70 and 415.20 is: 621.49

Step by Step Solution

  1. Step 1: Write the proportion equation
    428.70 : 641.70 = 415.20 : x
  2. Step 2: Convert to fraction form
    428.70/641.70 = 415.20/x
  3. Step 3: Cross multiply
    428.70x = 641.70 × 415.20
  4. Step 4: Simplify right side
    428.70x = 266,433.84
  5. Step 5: Solve for x
    x = 266,433.84/428.70
  6. Step 6: Final answer
    x = 621.49

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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.