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Finding the Fourth Proportional to 66.81, 100.21 and 21.19

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Solution

The fourth proportional to 66.81, 100.21 and 21.19 is: 31.79

Step by Step Solution

  1. Step 1: Write the proportion equation
    66.81 : 100.21 = 21.19 : x
  2. Step 2: Convert to fraction form
    66.81/100.21 = 21.19/x
  3. Step 3: Cross multiply
    66.81x = 100.21 × 21.19
  4. Step 4: Simplify right side
    66.81x = 2,123.72
  5. Step 5: Solve for x
    x = 2,123.72/66.81
  6. Step 6: Final answer
    x = 31.79

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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.