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Finding the Fourth Proportional to 78.81, 108.47 and 66.69

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Solution

The fourth proportional to 78.81, 108.47 and 66.69 is: 91.78

Step by Step Solution

  1. Step 1: Write the proportion equation
    78.81 : 108.47 = 66.69 : x
  2. Step 2: Convert to fraction form
    78.81/108.47 = 66.69/x
  3. Step 3: Cross multiply
    78.81x = 108.47 × 66.69
  4. Step 4: Simplify right side
    78.81x = 7,233.53
  5. Step 5: Solve for x
    x = 7,233.53/78.81
  6. Step 6: Final answer
    x = 91.78

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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.