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Finding the Fourth Proportional to 128.75, 177.59 and 87.30

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Solution

The fourth proportional to 128.75, 177.59 and 87.30 is: 120.42

Step by Step Solution

  1. Step 1: Write the proportion equation
    128.75 : 177.59 = 87.30 : x
  2. Step 2: Convert to fraction form
    128.75/177.59 = 87.30/x
  3. Step 3: Cross multiply
    128.75x = 177.59 × 87.30
  4. Step 4: Simplify right side
    128.75x = 15,503.83
  5. Step 5: Solve for x
    x = 15,503.83/128.75
  6. Step 6: Final answer
    x = 120.42

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Why These Related Problems?

These problems maintain the same ratio (1.38) or explore similar proportional relationships. Practicing with related ratios helps build understanding of proportional relationships.