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Finding the Fourth Proportional to 128.08, 191.76 and 84.70

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Solution

The fourth proportional to 128.08, 191.76 and 84.70 is: 126.81

Step by Step Solution

  1. Step 1: Write the proportion equation
    128.08 : 191.76 = 84.70 : x
  2. Step 2: Convert to fraction form
    128.08/191.76 = 84.70/x
  3. Step 3: Cross multiply
    128.08x = 191.76 × 84.70
  4. Step 4: Simplify right side
    128.08x = 16,242.07
  5. Step 5: Solve for x
    x = 16,242.07/128.08
  6. Step 6: Final answer
    x = 126.81

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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.