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Finding the Fourth Proportional to 85.41, 128.12 and 78.81

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Solution

The fourth proportional to 85.41, 128.12 and 78.81 is: 118.22

Step by Step Solution

  1. Step 1: Write the proportion equation
    85.41 : 128.12 = 78.81 : x
  2. Step 2: Convert to fraction form
    85.41/128.12 = 78.81/x
  3. Step 3: Cross multiply
    85.41x = 128.12 × 78.81
  4. Step 4: Simplify right side
    85.41x = 10,097.14
  5. Step 5: Solve for x
    x = 10,097.14/85.41
  6. Step 6: Final answer
    x = 118.22

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Why These Related Problems?

These problems maintain the same ratio (1.50) or explore similar proportional relationships. Practicing with related ratios helps build understanding of proportional relationships.