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Finding the Fourth Proportional to 128.51, 192.61 and 89.78

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Solution

The fourth proportional to 128.51, 192.61 and 89.78 is: 134.56

Step by Step Solution

  1. Step 1: Write the proportion equation
    128.51 : 192.61 = 89.78 : x
  2. Step 2: Convert to fraction form
    128.51/192.61 = 89.78/x
  3. Step 3: Cross multiply
    128.51x = 192.61 × 89.78
  4. Step 4: Simplify right side
    128.51x = 17,292.53
  5. Step 5: Solve for x
    x = 17,292.53/128.51
  6. Step 6: Final answer
    x = 134.56

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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.