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Finding the Fourth Proportional to 128.78, 193.21 and 71.00

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Solution

The fourth proportional to 128.78, 193.21 and 71.00 is: 106.51

Step by Step Solution

  1. Step 1: Write the proportion equation
    128.78 : 193.21 = 71.00 : x
  2. Step 2: Convert to fraction form
    128.78/193.21 = 71.00/x
  3. Step 3: Cross multiply
    128.78x = 193.21 × 71.00
  4. Step 4: Simplify right side
    128.78x = 13,716.77
  5. Step 5: Solve for x
    x = 13,716.77/128.78
  6. Step 6: Final answer
    x = 106.51

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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.