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Finding the Fourth Proportional to 21.09, 31.65 and 18.80

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Solution

The fourth proportional to 21.09, 31.65 and 18.80 is: 28.21

Step by Step Solution

  1. Step 1: Write the proportion equation
    21.09 : 31.65 = 18.80 : x
  2. Step 2: Convert to fraction form
    21.09/31.65 = 18.80/x
  3. Step 3: Cross multiply
    21.09x = 31.65 × 18.80
  4. Step 4: Simplify right side
    21.09x = 594.86
  5. Step 5: Solve for x
    x = 594.86/21.09
  6. Step 6: Final answer
    x = 28.21

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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.