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Finding the Fourth Proportional to 128.88, 177.86 and 76.42

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Solution

The fourth proportional to 128.88, 177.86 and 76.42 is: 105.45

Step by Step Solution

  1. Step 1: Write the proportion equation
    128.88 : 177.86 = 76.42 : x
  2. Step 2: Convert to fraction form
    128.88/177.86 = 76.42/x
  3. Step 3: Cross multiply
    128.88x = 177.86 × 76.42
  4. Step 4: Simplify right side
    128.88x = 13,590.79
  5. Step 5: Solve for x
    x = 13,590.79/128.88
  6. Step 6: Final answer
    x = 105.45

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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.