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Finding the Fourth Proportional to 21.13, 31.65 and 12.55

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Solution

The fourth proportional to 21.13, 31.65 and 12.55 is: 18.80

Step by Step Solution

  1. Step 1: Write the proportion equation
    21.13 : 31.65 = 12.55 : x
  2. Step 2: Convert to fraction form
    21.13/31.65 = 12.55/x
  3. Step 3: Cross multiply
    21.13x = 31.65 × 12.55
  4. Step 4: Simplify right side
    21.13x = 397.21
  5. Step 5: Solve for x
    x = 397.21/21.13
  6. Step 6: Final answer
    x = 18.80

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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.