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Finding the Fourth Proportional to 76.78, 105.64 and 66.39

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Solution

The fourth proportional to 76.78, 105.64 and 66.39 is: 91.34

Step by Step Solution

  1. Step 1: Write the proportion equation
    76.78 : 105.64 = 66.39 : x
  2. Step 2: Convert to fraction form
    76.78/105.64 = 66.39/x
  3. Step 3: Cross multiply
    76.78x = 105.64 × 66.39
  4. Step 4: Simplify right side
    76.78x = 7,012.88
  5. Step 5: Solve for x
    x = 7,012.88/76.78
  6. Step 6: Final answer
    x = 91.34

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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.