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Finding the Fourth Proportional to 81.24, 121.18 and 78.58

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Solution

The fourth proportional to 81.24, 121.18 and 78.58 is: 117.21

Step by Step Solution

  1. Step 1: Write the proportion equation
    81.24 : 121.18 = 78.58 : x
  2. Step 2: Convert to fraction form
    81.24/121.18 = 78.58/x
  3. Step 3: Cross multiply
    81.24x = 121.18 × 78.58
  4. Step 4: Simplify right side
    81.24x = 9,521.33
  5. Step 5: Solve for x
    x = 9,521.33/81.24
  6. Step 6: Final answer
    x = 117.21

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Why These Related Problems?

These problems maintain the same ratio (1.49) or explore similar proportional relationships. Practicing with related ratios helps build understanding of proportional relationships.