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Finding the Fourth Proportional to 128.42, 177.12 and 81.80

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Solution

The fourth proportional to 128.42, 177.12 and 81.80 is: 112.82

Step by Step Solution

  1. Step 1: Write the proportion equation
    128.42 : 177.12 = 81.80 : x
  2. Step 2: Convert to fraction form
    128.42/177.12 = 81.80/x
  3. Step 3: Cross multiply
    128.42x = 177.12 × 81.80
  4. Step 4: Simplify right side
    128.42x = 14,487.53
  5. Step 5: Solve for x
    x = 14,487.53/128.42
  6. Step 6: Final answer
    x = 112.82

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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.