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Finding the Fourth Proportional to 66.20, 91.31 and 39.98

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Solution

The fourth proportional to 66.20, 91.31 and 39.98 is: 55.14

Step by Step Solution

  1. Step 1: Write the proportion equation
    66.20 : 91.31 = 39.98 : x
  2. Step 2: Convert to fraction form
    66.20/91.31 = 39.98/x
  3. Step 3: Cross multiply
    66.20x = 91.31 × 39.98
  4. Step 4: Simplify right side
    66.20x = 3,649.92
  5. Step 5: Solve for x
    x = 3,649.92/66.20
  6. Step 6: Final answer
    x = 55.14

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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.