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Finding the Fourth Proportional to 128.10, 176.78 and 86.64

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Solution

The fourth proportional to 128.10, 176.78 and 86.64 is: 119.56

Step by Step Solution

  1. Step 1: Write the proportion equation
    128.10 : 176.78 = 86.64 : x
  2. Step 2: Convert to fraction form
    128.10/176.78 = 86.64/x
  3. Step 3: Cross multiply
    128.10x = 176.78 × 86.64
  4. Step 4: Simplify right side
    128.10x = 15,316.22
  5. Step 5: Solve for x
    x = 15,316.22/128.10
  6. Step 6: Final answer
    x = 119.56

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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.