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Finding the Fourth Proportional to 100.68, 138.90 and 61.86

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Solution

The fourth proportional to 100.68, 138.90 and 61.86 is: 85.34

Step by Step Solution

  1. Step 1: Write the proportion equation
    100.68 : 138.90 = 61.86 : x
  2. Step 2: Convert to fraction form
    100.68/138.90 = 61.86/x
  3. Step 3: Cross multiply
    100.68x = 138.90 × 61.86
  4. Step 4: Simplify right side
    100.68x = 8,592.35
  5. Step 5: Solve for x
    x = 8,592.35/100.68
  6. Step 6: Final answer
    x = 85.34

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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.