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Finding the Fourth Proportional to 138.91, 208.43 and 78.07

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Solution

The fourth proportional to 138.91, 208.43 and 78.07 is: 117.14

Step by Step Solution

  1. Step 1: Write the proportion equation
    138.91 : 208.43 = 78.07 : x
  2. Step 2: Convert to fraction form
    138.91/208.43 = 78.07/x
  3. Step 3: Cross multiply
    138.91x = 208.43 × 78.07
  4. Step 4: Simplify right side
    138.91x = 16,272.13
  5. Step 5: Solve for x
    x = 16,272.13/138.91
  6. Step 6: Final answer
    x = 117.14

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Why These Related Problems?

These problems maintain the same ratio (1.50) or explore similar proportional relationships. Practicing with related ratios helps build understanding of proportional relationships.