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Finding the Fourth Proportional to 31.90, 47.82 and 21.08

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Solution

The fourth proportional to 31.90, 47.82 and 21.08 is: 31.60

Step by Step Solution

  1. Step 1: Write the proportion equation
    31.90 : 47.82 = 21.08 : x
  2. Step 2: Convert to fraction form
    31.90/47.82 = 21.08/x
  3. Step 3: Cross multiply
    31.90x = 47.82 × 21.08
  4. Step 4: Simplify right side
    31.90x = 1,008.05
  5. Step 5: Solve for x
    x = 1,008.05/31.90
  6. Step 6: Final answer
    x = 31.60

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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.