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Finding the Fourth Proportional to 128.15, 191.90 and 87.56

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Solution

The fourth proportional to 128.15, 191.90 and 87.56 is: 131.12

Step by Step Solution

  1. Step 1: Write the proportion equation
    128.15 : 191.90 = 87.56 : x
  2. Step 2: Convert to fraction form
    128.15/191.90 = 87.56/x
  3. Step 3: Cross multiply
    128.15x = 191.90 × 87.56
  4. Step 4: Simplify right side
    128.15x = 16,802.02
  5. Step 5: Solve for x
    x = 16,802.02/128.15
  6. Step 6: Final answer
    x = 131.12

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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.