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Finding the Fourth Proportional to 190.40, 285.21 and 138.78

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Solution

The fourth proportional to 190.40, 285.21 and 138.78 is: 207.89

Step by Step Solution

  1. Step 1: Write the proportion equation
    190.40 : 285.21 = 138.78 : x
  2. Step 2: Convert to fraction form
    190.40/285.21 = 138.78/x
  3. Step 3: Cross multiply
    190.40x = 285.21 × 138.78
  4. Step 4: Simplify right side
    190.40x = 39,581.44
  5. Step 5: Solve for x
    x = 39,581.44/190.40
  6. Step 6: Final answer
    x = 207.89

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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.