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Finding the Fourth Proportional to 78.56, 108.72 and 76.40

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Solution

The fourth proportional to 78.56, 108.72 and 76.40 is: 105.73

Step by Step Solution

  1. Step 1: Write the proportion equation
    78.56 : 108.72 = 76.40 : x
  2. Step 2: Convert to fraction form
    78.56/108.72 = 76.40/x
  3. Step 3: Cross multiply
    78.56x = 108.72 × 76.40
  4. Step 4: Simplify right side
    78.56x = 8,306.21
  5. Step 5: Solve for x
    x = 8,306.21/78.56
  6. Step 6: Final answer
    x = 105.73

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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.