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Finding the Fourth Proportional to 429.88, 643.98 and 212.80

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Solution

The fourth proportional to 429.88, 643.98 and 212.80 is: 318.78

Step by Step Solution

  1. Step 1: Write the proportion equation
    429.88 : 643.98 = 212.80 : x
  2. Step 2: Convert to fraction form
    429.88/643.98 = 212.80/x
  3. Step 3: Cross multiply
    429.88x = 643.98 × 212.80
  4. Step 4: Simplify right side
    429.88x = 137,038.94
  5. Step 5: Solve for x
    x = 137,038.94/429.88
  6. Step 6: Final answer
    x = 318.78

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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.