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Finding the Fourth Proportional to 28.81, 39.78 and 21.58

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Solution

The fourth proportional to 28.81, 39.78 and 21.58 is: 29.80

Step by Step Solution

  1. Step 1: Write the proportion equation
    28.81 : 39.78 = 21.58 : x
  2. Step 2: Convert to fraction form
    28.81/39.78 = 21.58/x
  3. Step 3: Cross multiply
    28.81x = 39.78 × 21.58
  4. Step 4: Simplify right side
    28.81x = 858.45
  5. Step 5: Solve for x
    x = 858.45/28.81
  6. Step 6: Final answer
    x = 29.80

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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.