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Finding the Fourth Proportional to 102.98, 154.20 and 85.74

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Solution

The fourth proportional to 102.98, 154.20 and 85.74 is: 128.39

Step by Step Solution

  1. Step 1: Write the proportion equation
    102.98 : 154.20 = 85.74 : x
  2. Step 2: Convert to fraction form
    102.98/154.20 = 85.74/x
  3. Step 3: Cross multiply
    102.98x = 154.20 × 85.74
  4. Step 4: Simplify right side
    102.98x = 13,221.11
  5. Step 5: Solve for x
    x = 13,221.11/102.98
  6. Step 6: Final answer
    x = 128.39

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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.