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Finding the Fourth Proportional to 172.39, 258.71 and 81.15

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Solution

The fourth proportional to 172.39, 258.71 and 81.15 is: 121.79

Step by Step Solution

  1. Step 1: Write the proportion equation
    172.39 : 258.71 = 81.15 : x
  2. Step 2: Convert to fraction form
    172.39/258.71 = 81.15/x
  3. Step 3: Cross multiply
    172.39x = 258.71 × 81.15
  4. Step 4: Simplify right side
    172.39x = 20,994.52
  5. Step 5: Solve for x
    x = 20,994.52/172.39
  6. Step 6: Final answer
    x = 121.79

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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.