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Finding the Fourth Proportional to 28.90, 39.90 and 21.61

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Solution

The fourth proportional to 28.90, 39.90 and 21.61 is: 29.84

Step by Step Solution

  1. Step 1: Write the proportion equation
    28.90 : 39.90 = 21.61 : x
  2. Step 2: Convert to fraction form
    28.90/39.90 = 21.61/x
  3. Step 3: Cross multiply
    28.90x = 39.90 × 21.61
  4. Step 4: Simplify right side
    28.90x = 862.24
  5. Step 5: Solve for x
    x = 862.24/28.90
  6. Step 6: Final answer
    x = 29.84

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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.