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Finding the Fourth Proportional to 139.40, 192.38 and 81.21

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Solution

The fourth proportional to 139.40, 192.38 and 81.21 is: 112.08

Step by Step Solution

  1. Step 1: Write the proportion equation
    139.40 : 192.38 = 81.21 : x
  2. Step 2: Convert to fraction form
    139.40/192.38 = 81.21/x
  3. Step 3: Cross multiply
    139.40x = 192.38 × 81.21
  4. Step 4: Simplify right side
    139.40x = 15,622.77
  5. Step 5: Solve for x
    x = 15,622.77/139.40
  6. Step 6: Final answer
    x = 112.08

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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.