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Finding the Fourth Proportional to 81, 111.60 and 79.80

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Solution

The fourth proportional to 81, 111.60 and 79.80 is: 109.95

Step by Step Solution

  1. Step 1: Write the proportion equation
    81 : 111.60 = 79.80 : x
  2. Step 2: Convert to fraction form
    81/111.60 = 79.80/x
  3. Step 3: Cross multiply
    81x = 111.60 × 79.80
  4. Step 4: Simplify right side
    81x = 8,905.68
  5. Step 5: Solve for x
    x = 8,905.68/81
  6. Step 6: Final answer
    x = 109.95

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Why These Related Problems?

These problems maintain the same ratio (1.38) or explore similar proportional relationships. Practicing with related ratios helps build understanding of proportional relationships.