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Finding the Fourth Proportional to 100.47, 138.87 and 78.87

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Solution

The fourth proportional to 100.47, 138.87 and 78.87 is: 109.01

Step by Step Solution

  1. Step 1: Write the proportion equation
    100.47 : 138.87 = 78.87 : x
  2. Step 2: Convert to fraction form
    100.47/138.87 = 78.87/x
  3. Step 3: Cross multiply
    100.47x = 138.87 × 78.87
  4. Step 4: Simplify right side
    100.47x = 10,952.68
  5. Step 5: Solve for x
    x = 10,952.68/100.47
  6. Step 6: Final answer
    x = 109.01

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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.