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Finding the Fourth Proportional to 81.50, 121.58 and 78.96

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Solution

The fourth proportional to 81.50, 121.58 and 78.96 is: 117.79

Step by Step Solution

  1. Step 1: Write the proportion equation
    81.50 : 121.58 = 78.96 : x
  2. Step 2: Convert to fraction form
    81.50/121.58 = 78.96/x
  3. Step 3: Cross multiply
    81.50x = 121.58 × 78.96
  4. Step 4: Simplify right side
    81.50x = 9,599.56
  5. Step 5: Solve for x
    x = 9,599.56/81.50
  6. Step 6: Final answer
    x = 117.79

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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.