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Finding the Fourth Proportional to 86.09, 128.53 and 76.91

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Solution

The fourth proportional to 86.09, 128.53 and 76.91 is: 114.82

Step by Step Solution

  1. Step 1: Write the proportion equation
    86.09 : 128.53 = 76.91 : x
  2. Step 2: Convert to fraction form
    86.09/128.53 = 76.91/x
  3. Step 3: Cross multiply
    86.09x = 128.53 × 76.91
  4. Step 4: Simplify right side
    86.09x = 9,884.70
  5. Step 5: Solve for x
    x = 9,884.70/86.09
  6. Step 6: Final answer
    x = 114.82

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Why These Related Problems?

These problems maintain the same ratio (1.49) or explore similar proportional relationships. Practicing with related ratios helps build understanding of proportional relationships.