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Finding the Fourth Proportional to 86.12, 128.40 and 80.34

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Solution

The fourth proportional to 86.12, 128.40 and 80.34 is: 119.78

Step by Step Solution

  1. Step 1: Write the proportion equation
    86.12 : 128.40 = 80.34 : x
  2. Step 2: Convert to fraction form
    86.12/128.40 = 80.34/x
  3. Step 3: Cross multiply
    86.12x = 128.40 × 80.34
  4. Step 4: Simplify right side
    86.12x = 10,315.66
  5. Step 5: Solve for x
    x = 10,315.66/86.12
  6. Step 6: Final answer
    x = 119.78

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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.