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Finding the Fourth Proportional to 89.78, 123.90 and 57.05

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Solution

The fourth proportional to 89.78, 123.90 and 57.05 is: 78.73

Step by Step Solution

  1. Step 1: Write the proportion equation
    89.78 : 123.90 = 57.05 : x
  2. Step 2: Convert to fraction form
    89.78/123.90 = 57.05/x
  3. Step 3: Cross multiply
    89.78x = 123.90 × 57.05
  4. Step 4: Simplify right side
    89.78x = 7,067.88
  5. Step 5: Solve for x
    x = 7,067.88/89.78
  6. Step 6: Final answer
    x = 78.73

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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.