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Finding the Fourth Proportional to 128.70, 192.65 and 90

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Solution

The fourth proportional to 128.70, 192.65 and 90 is: 134.72

Step by Step Solution

  1. Step 1: Write the proportion equation
    128.70 : 192.65 = 90 : x
  2. Step 2: Convert to fraction form
    128.70/192.65 = 90/x
  3. Step 3: Cross multiply
    128.70x = 192.65 × 90
  4. Step 4: Simplify right side
    128.70x = 17,338.50
  5. Step 5: Solve for x
    x = 17,338.50/128.70
  6. Step 6: Final answer
    x = 134.72

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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.