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Finding the Fourth Proportional to 76.20, 105.30 and 61.72

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Solution

The fourth proportional to 76.20, 105.30 and 61.72 is: 85.29

Step by Step Solution

  1. Step 1: Write the proportion equation
    76.20 : 105.30 = 61.72 : x
  2. Step 2: Convert to fraction form
    76.20/105.30 = 61.72/x
  3. Step 3: Cross multiply
    76.20x = 105.30 × 61.72
  4. Step 4: Simplify right side
    76.20x = 6,499.12
  5. Step 5: Solve for x
    x = 6,499.12/76.20
  6. Step 6: Final answer
    x = 85.29

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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.