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Finding the Fourth Proportional to 31.80, 47.72 and 13.76

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Solution

The fourth proportional to 31.80, 47.72 and 13.76 is: 20.64

Step by Step Solution

  1. Step 1: Write the proportion equation
    31.80 : 47.72 = 13.76 : x
  2. Step 2: Convert to fraction form
    31.80/47.72 = 13.76/x
  3. Step 3: Cross multiply
    31.80x = 47.72 × 13.76
  4. Step 4: Simplify right side
    31.80x = 656.32
  5. Step 5: Solve for x
    x = 656.32/31.80
  6. Step 6: Final answer
    x = 20.64

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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.