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Finding the Fourth Proportional to 128.16, 191.70 and 87.39

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Solution

The fourth proportional to 128.16, 191.70 and 87.39 is: 130.72

Step by Step Solution

  1. Step 1: Write the proportion equation
    128.16 : 191.70 = 87.39 : x
  2. Step 2: Convert to fraction form
    128.16/191.70 = 87.39/x
  3. Step 3: Cross multiply
    128.16x = 191.70 × 87.39
  4. Step 4: Simplify right side
    128.16x = 16,752.66
  5. Step 5: Solve for x
    x = 16,752.66/128.16
  6. Step 6: Final answer
    x = 130.72

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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.