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Finding the Fourth Proportional to 90.45, 124.92 and 78.12

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Solution

The fourth proportional to 90.45, 124.92 and 78.12 is: 107.89

Step by Step Solution

  1. Step 1: Write the proportion equation
    90.45 : 124.92 = 78.12 : x
  2. Step 2: Convert to fraction form
    90.45/124.92 = 78.12/x
  3. Step 3: Cross multiply
    90.45x = 124.92 × 78.12
  4. Step 4: Simplify right side
    90.45x = 9,758.75
  5. Step 5: Solve for x
    x = 9,758.75/90.45
  6. Step 6: Final answer
    x = 107.89

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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.