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Finding the Fourth Proportional to 28.91, 39.93 and 20.78

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Solution

The fourth proportional to 28.91, 39.93 and 20.78 is: 28.70

Step by Step Solution

  1. Step 1: Write the proportion equation
    28.91 : 39.93 = 20.78 : x
  2. Step 2: Convert to fraction form
    28.91/39.93 = 20.78/x
  3. Step 3: Cross multiply
    28.91x = 39.93 × 20.78
  4. Step 4: Simplify right side
    28.91x = 829.64
  5. Step 5: Solve for x
    x = 829.64/28.91
  6. Step 6: Final answer
    x = 28.70

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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.