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Finding the Fourth Proportional to 111.66, 154.08 and 78.90

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Solution

The fourth proportional to 111.66, 154.08 and 78.90 is: 108.87

Step by Step Solution

  1. Step 1: Write the proportion equation
    111.66 : 154.08 = 78.90 : x
  2. Step 2: Convert to fraction form
    111.66/154.08 = 78.90/x
  3. Step 3: Cross multiply
    111.66x = 154.08 × 78.90
  4. Step 4: Simplify right side
    111.66x = 12,156.91
  5. Step 5: Solve for x
    x = 12,156.91/111.66
  6. Step 6: Final answer
    x = 108.87

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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.