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Finding the Fourth Proportional to 128,991.18, 178,007.85 and 72,420.78

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Solution

The fourth proportional to 128,991.18, 178,007.85 and 72,420.78 is: 99,940.69

Step by Step Solution

  1. Step 1: Write the proportion equation
    128,991.18 : 178,007.85 = 72,420.78 : x
  2. Step 2: Convert to fraction form
    128,991.18/178,007.85 = 72,420.78/x
  3. Step 3: Cross multiply
    128,991.18x = 178,007.85 × 72,420.78
  4. Step 4: Simplify right side
    128,991.18x = 12,891,467,343.12
  5. Step 5: Solve for x
    x = 12,891,467,343.12/128,991.18
  6. Step 6: Final answer
    x = 99,940.69

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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.