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Finding the Fourth Proportional to 139.68, 208.32 and 128.88

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Solution

The fourth proportional to 139.68, 208.32 and 128.88 is: 192.21

Step by Step Solution

  1. Step 1: Write the proportion equation
    139.68 : 208.32 = 128.88 : x
  2. Step 2: Convert to fraction form
    139.68/208.32 = 128.88/x
  3. Step 3: Cross multiply
    139.68x = 208.32 × 128.88
  4. Step 4: Simplify right side
    139.68x = 26,848.28
  5. Step 5: Solve for x
    x = 26,848.28/139.68
  6. Step 6: Final answer
    x = 192.21

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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.