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Finding the Fourth Proportional to 101.20, 139.75 and 78.12

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Solution

The fourth proportional to 101.20, 139.75 and 78.12 is: 107.87

Step by Step Solution

  1. Step 1: Write the proportion equation
    101.20 : 139.75 = 78.12 : x
  2. Step 2: Convert to fraction form
    101.20/139.75 = 78.12/x
  3. Step 3: Cross multiply
    101.20x = 139.75 × 78.12
  4. Step 4: Simplify right side
    101.20x = 10,916.57
  5. Step 5: Solve for x
    x = 10,916.57/101.20
  6. Step 6: Final answer
    x = 107.87

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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.