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Finding the Fourth Proportional to 428.79, 643.32 and 140.25

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Solution

The fourth proportional to 428.79, 643.32 and 140.25 is: 210.42

Step by Step Solution

  1. Step 1: Write the proportion equation
    428.79 : 643.32 = 140.25 : x
  2. Step 2: Convert to fraction form
    428.79/643.32 = 140.25/x
  3. Step 3: Cross multiply
    428.79x = 643.32 × 140.25
  4. Step 4: Simplify right side
    428.79x = 90,225.63
  5. Step 5: Solve for x
    x = 90,225.63/428.79
  6. Step 6: Final answer
    x = 210.42

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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.