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Finding the Fourth Proportional to 21.90, 32.85 and 12.88

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Solution

The fourth proportional to 21.90, 32.85 and 12.88 is: 19.32

Step by Step Solution

  1. Step 1: Write the proportion equation
    21.90 : 32.85 = 12.88 : x
  2. Step 2: Convert to fraction form
    21.90/32.85 = 12.88/x
  3. Step 3: Cross multiply
    21.90x = 32.85 × 12.88
  4. Step 4: Simplify right side
    21.90x = 423.11
  5. Step 5: Solve for x
    x = 423.11/21.90
  6. Step 6: Final answer
    x = 19.32

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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.