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Finding the Fourth Proportional to 128.12, 176.79 and 72.11

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Solution

The fourth proportional to 128.12, 176.79 and 72.11 is: 99.50

Step by Step Solution

  1. Step 1: Write the proportion equation
    128.12 : 176.79 = 72.11 : x
  2. Step 2: Convert to fraction form
    128.12/176.79 = 72.11/x
  3. Step 3: Cross multiply
    128.12x = 176.79 × 72.11
  4. Step 4: Simplify right side
    128.12x = 12,747.84
  5. Step 5: Solve for x
    x = 12,747.84/128.12
  6. Step 6: Final answer
    x = 99.50

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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.