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Finding the Fourth Proportional to 31.72, 47.56 and 21

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Solution

The fourth proportional to 31.72, 47.56 and 21 is: 31.49

Step by Step Solution

  1. Step 1: Write the proportion equation
    31.72 : 47.56 = 21 : x
  2. Step 2: Convert to fraction form
    31.72/47.56 = 21/x
  3. Step 3: Cross multiply
    31.72x = 47.56 × 21
  4. Step 4: Simplify right side
    31.72x = 998.76
  5. Step 5: Solve for x
    x = 998.76/31.72
  6. Step 6: Final answer
    x = 31.49

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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.