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Finding the Fourth Proportional to 115.17, 172.39 and 81

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Solution

The fourth proportional to 115.17, 172.39 and 81 is: 121.24

Step by Step Solution

  1. Step 1: Write the proportion equation
    115.17 : 172.39 = 81 : x
  2. Step 2: Convert to fraction form
    115.17/172.39 = 81/x
  3. Step 3: Cross multiply
    115.17x = 172.39 × 81
  4. Step 4: Simplify right side
    115.17x = 13,963.59
  5. Step 5: Solve for x
    x = 13,963.59/115.17
  6. Step 6: Final answer
    x = 121.24

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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.