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Finding the Fourth Proportional to 128.78, 177.69 and 77

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Solution

The fourth proportional to 128.78, 177.69 and 77 is: 106.24

Step by Step Solution

  1. Step 1: Write the proportion equation
    128.78 : 177.69 = 77 : x
  2. Step 2: Convert to fraction form
    128.78/177.69 = 77/x
  3. Step 3: Cross multiply
    128.78x = 177.69 × 77
  4. Step 4: Simplify right side
    128.78x = 13,682.13
  5. Step 5: Solve for x
    x = 13,682.13/128.78
  6. Step 6: Final answer
    x = 106.24

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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.