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Finding the Fourth Proportional to 28.45, 42.70 and 19.90

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Solution

The fourth proportional to 28.45, 42.70 and 19.90 is: 29.86

Step by Step Solution

  1. Step 1: Write the proportion equation
    28.45 : 42.70 = 19.90 : x
  2. Step 2: Convert to fraction form
    28.45/42.70 = 19.90/x
  3. Step 3: Cross multiply
    28.45x = 42.70 × 19.90
  4. Step 4: Simplify right side
    28.45x = 849.52
  5. Step 5: Solve for x
    x = 849.52/28.45
  6. Step 6: Final answer
    x = 29.86

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Why These Related Problems?

These problems maintain the same ratio (1.50) or explore similar proportional relationships. Practicing with related ratios helps build understanding of proportional relationships.