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Finding the Fourth Proportional to 100.60, 138.70 and 78.68

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Solution

The fourth proportional to 100.60, 138.70 and 78.68 is: 108.48

Step by Step Solution

  1. Step 1: Write the proportion equation
    100.60 : 138.70 = 78.68 : x
  2. Step 2: Convert to fraction form
    100.60/138.70 = 78.68/x
  3. Step 3: Cross multiply
    100.60x = 138.70 × 78.68
  4. Step 4: Simplify right side
    100.60x = 10,912.92
  5. Step 5: Solve for x
    x = 10,912.92/100.60
  6. Step 6: Final answer
    x = 108.48

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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.