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Finding the Fourth Proportional to 429.12, 643.41 and 212.85

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Solution

The fourth proportional to 429.12, 643.41 and 212.85 is: 319.14

Step by Step Solution

  1. Step 1: Write the proportion equation
    429.12 : 643.41 = 212.85 : x
  2. Step 2: Convert to fraction form
    429.12/643.41 = 212.85/x
  3. Step 3: Cross multiply
    429.12x = 643.41 × 212.85
  4. Step 4: Simplify right side
    429.12x = 136,949.82
  5. Step 5: Solve for x
    x = 136,949.82/429.12
  6. Step 6: Final answer
    x = 319.14

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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.