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Finding the Fourth Proportional to 122.40, 168.96 and 81

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Solution

The fourth proportional to 122.40, 168.96 and 81 is: 111.81

Step by Step Solution

  1. Step 1: Write the proportion equation
    122.40 : 168.96 = 81 : x
  2. Step 2: Convert to fraction form
    122.40/168.96 = 81/x
  3. Step 3: Cross multiply
    122.40x = 168.96 × 81
  4. Step 4: Simplify right side
    122.40x = 13,685.76
  5. Step 5: Solve for x
    x = 13,685.76/122.40
  6. Step 6: Final answer
    x = 111.81

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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.