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Finding the Fourth Proportional to 128.47, 177.06 and 86.99

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Solution

The fourth proportional to 128.47, 177.06 and 86.99 is: 119.90

Step by Step Solution

  1. Step 1: Write the proportion equation
    128.47 : 177.06 = 86.99 : x
  2. Step 2: Convert to fraction form
    128.47/177.06 = 86.99/x
  3. Step 3: Cross multiply
    128.47x = 177.06 × 86.99
  4. Step 4: Simplify right side
    128.47x = 15,402.45
  5. Step 5: Solve for x
    x = 15,402.45/128.47
  6. Step 6: Final answer
    x = 119.90

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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.