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Finding the Fourth Proportional to 42.78, 64.17 and 19.94

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Solution

The fourth proportional to 42.78, 64.17 and 19.94 is: 29.90

Step by Step Solution

  1. Step 1: Write the proportion equation
    42.78 : 64.17 = 19.94 : x
  2. Step 2: Convert to fraction form
    42.78/64.17 = 19.94/x
  3. Step 3: Cross multiply
    42.78x = 64.17 × 19.94
  4. Step 4: Simplify right side
    42.78x = 1,279.13
  5. Step 5: Solve for x
    x = 1,279.13/42.78
  6. Step 6: Final answer
    x = 29.90

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Why These Related Problems?

These problems maintain the same ratio (1.50) or explore similar proportional relationships. Practicing with related ratios helps build understanding of proportional relationships.