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Finding the Fourth Proportional to 100.20, 138.28 and 61.40

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Solution

The fourth proportional to 100.20, 138.28 and 61.40 is: 84.73

Step by Step Solution

  1. Step 1: Write the proportion equation
    100.20 : 138.28 = 61.40 : x
  2. Step 2: Convert to fraction form
    100.20/138.28 = 61.40/x
  3. Step 3: Cross multiply
    100.20x = 138.28 × 61.40
  4. Step 4: Simplify right side
    100.20x = 8,490.39
  5. Step 5: Solve for x
    x = 8,490.39/100.20
  6. Step 6: Final answer
    x = 84.73

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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.