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Finding the Fourth Proportional to 78.86, 108.78 and 66.64

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Solution

The fourth proportional to 78.86, 108.78 and 66.64 is: 91.92

Step by Step Solution

  1. Step 1: Write the proportion equation
    78.86 : 108.78 = 66.64 : x
  2. Step 2: Convert to fraction form
    78.86/108.78 = 66.64/x
  3. Step 3: Cross multiply
    78.86x = 108.78 × 66.64
  4. Step 4: Simplify right side
    78.86x = 7,249.10
  5. Step 5: Solve for x
    x = 7,249.10/78.86
  6. Step 6: Final answer
    x = 91.92

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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.