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Finding the Fourth Proportional to 128.81, 177.50 and 85.07

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Solution

The fourth proportional to 128.81, 177.50 and 85.07 is: 117.22

Step by Step Solution

  1. Step 1: Write the proportion equation
    128.81 : 177.50 = 85.07 : x
  2. Step 2: Convert to fraction form
    128.81/177.50 = 85.07/x
  3. Step 3: Cross multiply
    128.81x = 177.50 × 85.07
  4. Step 4: Simplify right side
    128.81x = 15,099.04
  5. Step 5: Solve for x
    x = 15,099.04/128.81
  6. Step 6: Final answer
    x = 117.22

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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.