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Finding the Fourth Proportional to 139.70, 209.28 and 91.64

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Solution

The fourth proportional to 139.70, 209.28 and 91.64 is: 137.28

Step by Step Solution

  1. Step 1: Write the proportion equation
    139.70 : 209.28 = 91.64 : x
  2. Step 2: Convert to fraction form
    139.70/209.28 = 91.64/x
  3. Step 3: Cross multiply
    139.70x = 209.28 × 91.64
  4. Step 4: Simplify right side
    139.70x = 19,178.42
  5. Step 5: Solve for x
    x = 19,178.42/139.70
  6. Step 6: Final answer
    x = 137.28

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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.