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Finding the Fourth Proportional to 428.86, 643.38 and 140.28

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Solution

The fourth proportional to 428.86, 643.38 and 140.28 is: 210.45

Step by Step Solution

  1. Step 1: Write the proportion equation
    428.86 : 643.38 = 140.28 : x
  2. Step 2: Convert to fraction form
    428.86/643.38 = 140.28/x
  3. Step 3: Cross multiply
    428.86x = 643.38 × 140.28
  4. Step 4: Simplify right side
    428.86x = 90,253.35
  5. Step 5: Solve for x
    x = 90,253.35/428.86
  6. Step 6: Final answer
    x = 210.45

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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.