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Finding the Fourth Proportional to 31.76, 47.42 and 28.72

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Solution

The fourth proportional to 31.76, 47.42 and 28.72 is: 42.88

Step by Step Solution

  1. Step 1: Write the proportion equation
    31.76 : 47.42 = 28.72 : x
  2. Step 2: Convert to fraction form
    31.76/47.42 = 28.72/x
  3. Step 3: Cross multiply
    31.76x = 47.42 × 28.72
  4. Step 4: Simplify right side
    31.76x = 1,361.90
  5. Step 5: Solve for x
    x = 1,361.90/31.76
  6. Step 6: Final answer
    x = 42.88

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Why These Related Problems?

These problems maintain the same ratio (1.49) or explore similar proportional relationships. Practicing with related ratios helps build understanding of proportional relationships.