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Finding the Fourth Proportional to 139.90, 209.78 and 66.77

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Solution

The fourth proportional to 139.90, 209.78 and 66.77 is: 100.13

Step by Step Solution

  1. Step 1: Write the proportion equation
    139.90 : 209.78 = 66.77 : x
  2. Step 2: Convert to fraction form
    139.90/209.78 = 66.77/x
  3. Step 3: Cross multiply
    139.90x = 209.78 × 66.77
  4. Step 4: Simplify right side
    139.90x = 14,007.01
  5. Step 5: Solve for x
    x = 14,007.01/139.90
  6. Step 6: Final answer
    x = 100.13

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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.