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Finding the Fourth Proportional to 39.21, 58.72 and 21.18

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Solution

The fourth proportional to 39.21, 58.72 and 21.18 is: 31.72

Step by Step Solution

  1. Step 1: Write the proportion equation
    39.21 : 58.72 = 21.18 : x
  2. Step 2: Convert to fraction form
    39.21/58.72 = 21.18/x
  3. Step 3: Cross multiply
    39.21x = 58.72 × 21.18
  4. Step 4: Simplify right side
    39.21x = 1,243.69
  5. Step 5: Solve for x
    x = 1,243.69/39.21
  6. Step 6: Final answer
    x = 31.72

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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.