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Finding the Fourth Proportional to 20.72, 30.90 and 20.45

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Solution

The fourth proportional to 20.72, 30.90 and 20.45 is: 30.50

Step by Step Solution

  1. Step 1: Write the proportion equation
    20.72 : 30.90 = 20.45 : x
  2. Step 2: Convert to fraction form
    20.72/30.90 = 20.45/x
  3. Step 3: Cross multiply
    20.72x = 30.90 × 20.45
  4. Step 4: Simplify right side
    20.72x = 631.91
  5. Step 5: Solve for x
    x = 631.91/20.72
  6. Step 6: Final answer
    x = 30.50

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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.