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Finding the Fourth Proportional to 31.79, 47.72 and 21.11

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Solution

The fourth proportional to 31.79, 47.72 and 21.11 is: 31.68

Step by Step Solution

  1. Step 1: Write the proportion equation
    31.79 : 47.72 = 21.11 : x
  2. Step 2: Convert to fraction form
    31.79/47.72 = 21.11/x
  3. Step 3: Cross multiply
    31.79x = 47.72 × 21.11
  4. Step 4: Simplify right side
    31.79x = 1,007.26
  5. Step 5: Solve for x
    x = 1,007.26/31.79
  6. Step 6: Final answer
    x = 31.68

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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.