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Finding the Fourth Proportional to 31.72, 43.75 and 20.78

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Solution

The fourth proportional to 31.72, 43.75 and 20.78 is: 28.67

Step by Step Solution

  1. Step 1: Write the proportion equation
    31.72 : 43.75 = 20.78 : x
  2. Step 2: Convert to fraction form
    31.72/43.75 = 20.78/x
  3. Step 3: Cross multiply
    31.72x = 43.75 × 20.78
  4. Step 4: Simplify right side
    31.72x = 909.26
  5. Step 5: Solve for x
    x = 909.26/31.72
  6. Step 6: Final answer
    x = 28.67

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Why These Related Problems?

These problems maintain the same ratio (1.38) or explore similar proportional relationships. Practicing with related ratios helps build understanding of proportional relationships.