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Finding the Fourth Proportional to 128.57, 177.48 and 87.12

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Solution

The fourth proportional to 128.57, 177.48 and 87.12 is: 120.27

Step by Step Solution

  1. Step 1: Write the proportion equation
    128.57 : 177.48 = 87.12 : x
  2. Step 2: Convert to fraction form
    128.57/177.48 = 87.12/x
  3. Step 3: Cross multiply
    128.57x = 177.48 × 87.12
  4. Step 4: Simplify right side
    128.57x = 15,462.06
  5. Step 5: Solve for x
    x = 15,462.06/128.57
  6. Step 6: Final answer
    x = 120.27

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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.