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Finding the Fourth Proportional to 128.09, 191.79 and 105

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Solution

The fourth proportional to 128.09, 191.79 and 105 is: 157.22

Step by Step Solution

  1. Step 1: Write the proportion equation
    128.09 : 191.79 = 105 : x
  2. Step 2: Convert to fraction form
    128.09/191.79 = 105/x
  3. Step 3: Cross multiply
    128.09x = 191.79 × 105
  4. Step 4: Simplify right side
    128.09x = 20,137.95
  5. Step 5: Solve for x
    x = 20,137.95/128.09
  6. Step 6: Final answer
    x = 157.22

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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.