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Finding the Fourth Proportional to 100.67, 138.88 and 78.90

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Solution

The fourth proportional to 100.67, 138.88 and 78.90 is: 108.85

Step by Step Solution

  1. Step 1: Write the proportion equation
    100.67 : 138.88 = 78.90 : x
  2. Step 2: Convert to fraction form
    100.67/138.88 = 78.90/x
  3. Step 3: Cross multiply
    100.67x = 138.88 × 78.90
  4. Step 4: Simplify right side
    100.67x = 10,957.63
  5. Step 5: Solve for x
    x = 10,957.63/100.67
  6. Step 6: Final answer
    x = 108.85

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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.