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Finding the Fourth Proportional to 128.12, 191.99 and 67.21

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Solution

The fourth proportional to 128.12, 191.99 and 67.21 is: 100.72

Step by Step Solution

  1. Step 1: Write the proportion equation
    128.12 : 191.99 = 67.21 : x
  2. Step 2: Convert to fraction form
    128.12/191.99 = 67.21/x
  3. Step 3: Cross multiply
    128.12x = 191.99 × 67.21
  4. Step 4: Simplify right side
    128.12x = 12,903.34
  5. Step 5: Solve for x
    x = 12,903.34/128.12
  6. Step 6: Final answer
    x = 100.72

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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.