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Finding the Fourth Proportional to 78.81, 108.78 and 47.75

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Solution

The fourth proportional to 78.81, 108.78 and 47.75 is: 65.90

Step by Step Solution

  1. Step 1: Write the proportion equation
    78.81 : 108.78 = 47.75 : x
  2. Step 2: Convert to fraction form
    78.81/108.78 = 47.75/x
  3. Step 3: Cross multiply
    78.81x = 108.78 × 47.75
  4. Step 4: Simplify right side
    78.81x = 5,193.70
  5. Step 5: Solve for x
    x = 5,193.70/78.81
  6. Step 6: Final answer
    x = 65.90

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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.