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Finding the Fourth Proportional to 102.92, 142.21 and 78.31

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Solution

The fourth proportional to 102.92, 142.21 and 78.31 is: 108.21

Step by Step Solution

  1. Step 1: Write the proportion equation
    102.92 : 142.21 = 78.31 : x
  2. Step 2: Convert to fraction form
    102.92/142.21 = 78.31/x
  3. Step 3: Cross multiply
    102.92x = 142.21 × 78.31
  4. Step 4: Simplify right side
    102.92x = 11,136.47
  5. Step 5: Solve for x
    x = 11,136.47/102.92
  6. Step 6: Final answer
    x = 108.21

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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.