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Finding the Fourth Proportional to 138.96, 191.75 and 87.21

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Solution

The fourth proportional to 138.96, 191.75 and 87.21 is: 120.34

Step by Step Solution

  1. Step 1: Write the proportion equation
    138.96 : 191.75 = 87.21 : x
  2. Step 2: Convert to fraction form
    138.96/191.75 = 87.21/x
  3. Step 3: Cross multiply
    138.96x = 191.75 × 87.21
  4. Step 4: Simplify right side
    138.96x = 16,722.08
  5. Step 5: Solve for x
    x = 16,722.08/138.96
  6. Step 6: Final answer
    x = 120.34

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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.