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Finding the Fourth Proportional to 138.28, 206.40 and 128.76

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Solution

The fourth proportional to 138.28, 206.40 and 128.76 is: 192.19

Step by Step Solution

  1. Step 1: Write the proportion equation
    138.28 : 206.40 = 128.76 : x
  2. Step 2: Convert to fraction form
    138.28/206.40 = 128.76/x
  3. Step 3: Cross multiply
    138.28x = 206.40 × 128.76
  4. Step 4: Simplify right side
    138.28x = 26,576.06
  5. Step 5: Solve for x
    x = 26,576.06/138.28
  6. Step 6: Final answer
    x = 192.19

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Why These Related Problems?

These problems maintain the same ratio (1.49) or explore similar proportional relationships. Practicing with related ratios helps build understanding of proportional relationships.