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Finding the Fourth Proportional to 128.77, 177.69 and 76.31

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Solution

The fourth proportional to 128.77, 177.69 and 76.31 is: 105.30

Step by Step Solution

  1. Step 1: Write the proportion equation
    128.77 : 177.69 = 76.31 : x
  2. Step 2: Convert to fraction form
    128.77/177.69 = 76.31/x
  3. Step 3: Cross multiply
    128.77x = 177.69 × 76.31
  4. Step 4: Simplify right side
    128.77x = 13,559.52
  5. Step 5: Solve for x
    x = 13,559.52/128.77
  6. Step 6: Final answer
    x = 105.30

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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.