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Finding the Fourth Proportional to 438, 656.90 and 129.78

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Solution

The fourth proportional to 438, 656.90 and 129.78 is: 194.64

Step by Step Solution

  1. Step 1: Write the proportion equation
    438 : 656.90 = 129.78 : x
  2. Step 2: Convert to fraction form
    438/656.90 = 129.78/x
  3. Step 3: Cross multiply
    438x = 656.90 × 129.78
  4. Step 4: Simplify right side
    438x = 85,252.48
  5. Step 5: Solve for x
    x = 85,252.48/438
  6. Step 6: Final answer
    x = 194.64

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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.