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Finding the Fourth Proportional to 128.80, 193.20 and 71.20

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Solution

The fourth proportional to 128.80, 193.20 and 71.20 is: 106.80

Step by Step Solution

  1. Step 1: Write the proportion equation
    128.80 : 193.20 = 71.20 : x
  2. Step 2: Convert to fraction form
    128.80/193.20 = 71.20/x
  3. Step 3: Cross multiply
    128.80x = 193.20 × 71.20
  4. Step 4: Simplify right side
    128.80x = 13,755.84
  5. Step 5: Solve for x
    x = 13,755.84/128.80
  6. Step 6: Final answer
    x = 106.80

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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.