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Finding the Fourth Proportional to 100.39, 138.39 and 78.19

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Solution

The fourth proportional to 100.39, 138.39 and 78.19 is: 107.79

Step by Step Solution

  1. Step 1: Write the proportion equation
    100.39 : 138.39 = 78.19 : x
  2. Step 2: Convert to fraction form
    100.39/138.39 = 78.19/x
  3. Step 3: Cross multiply
    100.39x = 138.39 × 78.19
  4. Step 4: Simplify right side
    100.39x = 10,820.02
  5. Step 5: Solve for x
    x = 10,820.02/100.39
  6. Step 6: Final answer
    x = 107.79

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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.