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Finding the Fourth Proportional to 139.65, 209.38 and 78.81

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Solution

The fourth proportional to 139.65, 209.38 and 78.81 is: 118.16

Step by Step Solution

  1. Step 1: Write the proportion equation
    139.65 : 209.38 = 78.81 : x
  2. Step 2: Convert to fraction form
    139.65/209.38 = 78.81/x
  3. Step 3: Cross multiply
    139.65x = 209.38 × 78.81
  4. Step 4: Simplify right side
    139.65x = 16,501.24
  5. Step 5: Solve for x
    x = 16,501.24/139.65
  6. Step 6: Final answer
    x = 118.16

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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.