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Finding the Fourth Proportional to 128.21, 192.31 and 51.15

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Solution

The fourth proportional to 128.21, 192.31 and 51.15 is: 76.72

Step by Step Solution

  1. Step 1: Write the proportion equation
    128.21 : 192.31 = 51.15 : x
  2. Step 2: Convert to fraction form
    128.21/192.31 = 51.15/x
  3. Step 3: Cross multiply
    128.21x = 192.31 × 51.15
  4. Step 4: Simplify right side
    128.21x = 9,836.66
  5. Step 5: Solve for x
    x = 9,836.66/128.21
  6. Step 6: Final answer
    x = 76.72

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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.