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Finding the Fourth Proportional to 139.72, 192.80 and 81.50

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Solution

The fourth proportional to 139.72, 192.80 and 81.50 is: 112.46

Step by Step Solution

  1. Step 1: Write the proportion equation
    139.72 : 192.80 = 81.50 : x
  2. Step 2: Convert to fraction form
    139.72/192.80 = 81.50/x
  3. Step 3: Cross multiply
    139.72x = 192.80 × 81.50
  4. Step 4: Simplify right side
    139.72x = 15,713.20
  5. Step 5: Solve for x
    x = 15,713.20/139.72
  6. Step 6: Final answer
    x = 112.46

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Why These Related Problems?

These problems maintain the same ratio (1.38) or explore similar proportional relationships. Practicing with related ratios helps build understanding of proportional relationships.