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Finding the Fourth Proportional to 47.85, 71.75 and 20.81

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Solution

The fourth proportional to 47.85, 71.75 and 20.81 is: 31.19

Step by Step Solution

  1. Step 1: Write the proportion equation
    47.85 : 71.75 = 20.81 : x
  2. Step 2: Convert to fraction form
    47.85/71.75 = 20.81/x
  3. Step 3: Cross multiply
    47.85x = 71.75 × 20.81
  4. Step 4: Simplify right side
    47.85x = 1,492.65
  5. Step 5: Solve for x
    x = 1,492.65/47.85
  6. Step 6: Final answer
    x = 31.19

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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.