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Finding the Fourth Proportional to 428.80, 643.20 and 140.24

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Solution

The fourth proportional to 428.80, 643.20 and 140.24 is: 210.36

Step by Step Solution

  1. Step 1: Write the proportion equation
    428.80 : 643.20 = 140.24 : x
  2. Step 2: Convert to fraction form
    428.80/643.20 = 140.24/x
  3. Step 3: Cross multiply
    428.80x = 643.20 × 140.24
  4. Step 4: Simplify right side
    428.80x = 90,202.37
  5. Step 5: Solve for x
    x = 90,202.37/428.80
  6. Step 6: Final answer
    x = 210.36

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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.