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Finding the Fourth Proportional to 128, 176.68 and 81.45

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Solution

The fourth proportional to 128, 176.68 and 81.45 is: 112.43

Step by Step Solution

  1. Step 1: Write the proportion equation
    128 : 176.68 = 81.45 : x
  2. Step 2: Convert to fraction form
    128/176.68 = 81.45/x
  3. Step 3: Cross multiply
    128x = 176.68 × 81.45
  4. Step 4: Simplify right side
    128x = 14,390.59
  5. Step 5: Solve for x
    x = 14,390.59/128
  6. Step 6: Final answer
    x = 112.43

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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.