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Finding the Fourth Proportional to 139.68, 209.32 and 78.50

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Solution

The fourth proportional to 139.68, 209.32 and 78.50 is: 117.64

Step by Step Solution

  1. Step 1: Write the proportion equation
    139.68 : 209.32 = 78.50 : x
  2. Step 2: Convert to fraction form
    139.68/209.32 = 78.50/x
  3. Step 3: Cross multiply
    139.68x = 209.32 × 78.50
  4. Step 4: Simplify right side
    139.68x = 16,432.24
  5. Step 5: Solve for x
    x = 16,432.24/139.68
  6. Step 6: Final answer
    x = 117.64

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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.