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Finding the Fourth Proportional to 81.36, 121.19 and 78.80

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Solution

The fourth proportional to 81.36, 121.19 and 78.80 is: 117.36

Step by Step Solution

  1. Step 1: Write the proportion equation
    81.36 : 121.19 = 78.80 : x
  2. Step 2: Convert to fraction form
    81.36/121.19 = 78.80/x
  3. Step 3: Cross multiply
    81.36x = 121.19 × 78.80
  4. Step 4: Simplify right side
    81.36x = 9,548.77
  5. Step 5: Solve for x
    x = 9,548.77/81.36
  6. Step 6: Final answer
    x = 117.36

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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.