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Finding the Fourth Proportional to 128, 191.88 and 87.32

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Solution

The fourth proportional to 128, 191.88 and 87.32 is: 130.90

Step by Step Solution

  1. Step 1: Write the proportion equation
    128 : 191.88 = 87.32 : x
  2. Step 2: Convert to fraction form
    128/191.88 = 87.32/x
  3. Step 3: Cross multiply
    128x = 191.88 × 87.32
  4. Step 4: Simplify right side
    128x = 16,754.96
  5. Step 5: Solve for x
    x = 16,754.96/128
  6. Step 6: Final answer
    x = 130.90

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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.