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Finding the Fourth Proportional to 139.68, 209.76 and 91.68

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Solution

The fourth proportional to 139.68, 209.76 and 91.68 is: 137.68

Step by Step Solution

  1. Step 1: Write the proportion equation
    139.68 : 209.76 = 91.68 : x
  2. Step 2: Convert to fraction form
    139.68/209.76 = 91.68/x
  3. Step 3: Cross multiply
    139.68x = 209.76 × 91.68
  4. Step 4: Simplify right side
    139.68x = 19,230.80
  5. Step 5: Solve for x
    x = 19,230.80/139.68
  6. Step 6: Final answer
    x = 137.68

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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.