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Finding the Fourth Proportional to 428.34, 641.78 and 386.86

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Solution

The fourth proportional to 428.34, 641.78 and 386.86 is: 579.63

Step by Step Solution

  1. Step 1: Write the proportion equation
    428.34 : 641.78 = 386.86 : x
  2. Step 2: Convert to fraction form
    428.34/641.78 = 386.86/x
  3. Step 3: Cross multiply
    428.34x = 641.78 × 386.86
  4. Step 4: Simplify right side
    428.34x = 248,279.01
  5. Step 5: Solve for x
    x = 248,279.01/428.34
  6. Step 6: Final answer
    x = 579.63

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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.