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Finding the Fourth Proportional to 21.78, 32.65 and 12.15

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Solution

The fourth proportional to 21.78, 32.65 and 12.15 is: 18.21

Step by Step Solution

  1. Step 1: Write the proportion equation
    21.78 : 32.65 = 12.15 : x
  2. Step 2: Convert to fraction form
    21.78/32.65 = 12.15/x
  3. Step 3: Cross multiply
    21.78x = 32.65 × 12.15
  4. Step 4: Simplify right side
    21.78x = 396.70
  5. Step 5: Solve for x
    x = 396.70/21.78
  6. Step 6: Final answer
    x = 18.21

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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.