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Finding the Fourth Proportional to 31.14, 42.98 and 20.78

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Solution

The fourth proportional to 31.14, 42.98 and 20.78 is: 28.68

Step by Step Solution

  1. Step 1: Write the proportion equation
    31.14 : 42.98 = 20.78 : x
  2. Step 2: Convert to fraction form
    31.14/42.98 = 20.78/x
  3. Step 3: Cross multiply
    31.14x = 42.98 × 20.78
  4. Step 4: Simplify right side
    31.14x = 893.02
  5. Step 5: Solve for x
    x = 893.02/31.14
  6. Step 6: Final answer
    x = 28.68

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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.