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Finding the Fourth Proportional to 111.90, 154.35 and 78.70

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Solution

The fourth proportional to 111.90, 154.35 and 78.70 is: 108.56

Step by Step Solution

  1. Step 1: Write the proportion equation
    111.90 : 154.35 = 78.70 : x
  2. Step 2: Convert to fraction form
    111.90/154.35 = 78.70/x
  3. Step 3: Cross multiply
    111.90x = 154.35 × 78.70
  4. Step 4: Simplify right side
    111.90x = 12,147.35
  5. Step 5: Solve for x
    x = 12,147.35/111.90
  6. Step 6: Final answer
    x = 108.56

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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.