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Finding the Fourth Proportional to 128.46, 177.36 and 100.78

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Solution

The fourth proportional to 128.46, 177.36 and 100.78 is: 139.14

Step by Step Solution

  1. Step 1: Write the proportion equation
    128.46 : 177.36 = 100.78 : x
  2. Step 2: Convert to fraction form
    128.46/177.36 = 100.78/x
  3. Step 3: Cross multiply
    128.46x = 177.36 × 100.78
  4. Step 4: Simplify right side
    128.46x = 17,874.37
  5. Step 5: Solve for x
    x = 17,874.37/128.46
  6. Step 6: Final answer
    x = 139.14

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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.