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Finding the Fourth Proportional to 139.92, 209.76 and 71.40

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Solution

The fourth proportional to 139.92, 209.76 and 71.40 is: 107.04

Step by Step Solution

  1. Step 1: Write the proportion equation
    139.92 : 209.76 = 71.40 : x
  2. Step 2: Convert to fraction form
    139.92/209.76 = 71.40/x
  3. Step 3: Cross multiply
    139.92x = 209.76 × 71.40
  4. Step 4: Simplify right side
    139.92x = 14,976.86
  5. Step 5: Solve for x
    x = 14,976.86/139.92
  6. Step 6: Final answer
    x = 107.04

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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.