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Finding the Fourth Proportional to 28.70, 39.61 and 21.42

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Solution

The fourth proportional to 28.70, 39.61 and 21.42 is: 29.56

Step by Step Solution

  1. Step 1: Write the proportion equation
    28.70 : 39.61 = 21.42 : x
  2. Step 2: Convert to fraction form
    28.70/39.61 = 21.42/x
  3. Step 3: Cross multiply
    28.70x = 39.61 × 21.42
  4. Step 4: Simplify right side
    28.70x = 848.45
  5. Step 5: Solve for x
    x = 848.45/28.70
  6. Step 6: Final answer
    x = 29.56

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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.