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Finding the Fourth Proportional to 172.39, 258.60 and 85.81

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Solution

The fourth proportional to 172.39, 258.60 and 85.81 is: 128.72

Step by Step Solution

  1. Step 1: Write the proportion equation
    172.39 : 258.60 = 85.81 : x
  2. Step 2: Convert to fraction form
    172.39/258.60 = 85.81/x
  3. Step 3: Cross multiply
    172.39x = 258.60 × 85.81
  4. Step 4: Simplify right side
    172.39x = 22,190.47
  5. Step 5: Solve for x
    x = 22,190.47/172.39
  6. Step 6: Final answer
    x = 128.72

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Why These Related Problems?

These problems maintain the same ratio (1.50) or explore similar proportional relationships. Practicing with related ratios helps build understanding of proportional relationships.