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Finding the Fourth Proportional to 129.50, 178.73 and 90.21

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Solution

The fourth proportional to 129.50, 178.73 and 90.21 is: 124.50

Step by Step Solution

  1. Step 1: Write the proportion equation
    129.50 : 178.73 = 90.21 : x
  2. Step 2: Convert to fraction form
    129.50/178.73 = 90.21/x
  3. Step 3: Cross multiply
    129.50x = 178.73 × 90.21
  4. Step 4: Simplify right side
    129.50x = 16,123.23
  5. Step 5: Solve for x
    x = 16,123.23/129.50
  6. Step 6: Final answer
    x = 124.50

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Why These Related Problems?

These problems maintain the same ratio (1.38) or explore similar proportional relationships. Practicing with related ratios helps build understanding of proportional relationships.