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Finding the Fourth Proportional to 31.80, 47.69 and 13.79

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Solution

The fourth proportional to 31.80, 47.69 and 13.79 is: 20.67

Step by Step Solution

  1. Step 1: Write the proportion equation
    31.80 : 47.69 = 13.79 : x
  2. Step 2: Convert to fraction form
    31.80/47.69 = 13.79/x
  3. Step 3: Cross multiply
    31.80x = 47.69 × 13.79
  4. Step 4: Simplify right side
    31.80x = 657.34
  5. Step 5: Solve for x
    x = 657.34/31.80
  6. Step 6: Final answer
    x = 20.67

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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.