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Finding the Fourth Proportional to 66.40, 99.61 and 20.76

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Solution

The fourth proportional to 66.40, 99.61 and 20.76 is: 31.14

Step by Step Solution

  1. Step 1: Write the proportion equation
    66.40 : 99.61 = 20.76 : x
  2. Step 2: Convert to fraction form
    66.40/99.61 = 20.76/x
  3. Step 3: Cross multiply
    66.40x = 99.61 × 20.76
  4. Step 4: Simplify right side
    66.40x = 2,067.85
  5. Step 5: Solve for x
    x = 2,067.85/66.40
  6. Step 6: Final answer
    x = 31.14

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Why These Related Problems?

These problems maintain the same ratio (1.50) or explore similar proportional relationships. Practicing with related ratios helps build understanding of proportional relationships.