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Finding the Fourth Proportional to 28.78, 39.71 and 21.86

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Solution

The fourth proportional to 28.78, 39.71 and 21.86 is: 30.16

Step by Step Solution

  1. Step 1: Write the proportion equation
    28.78 : 39.71 = 21.86 : x
  2. Step 2: Convert to fraction form
    28.78/39.71 = 21.86/x
  3. Step 3: Cross multiply
    28.78x = 39.71 × 21.86
  4. Step 4: Simplify right side
    28.78x = 868.06
  5. Step 5: Solve for x
    x = 868.06/28.78
  6. Step 6: Final answer
    x = 30.16

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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.