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Finding the Fourth Proportional to 21.15, 29.20 and 13.88

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Solution

The fourth proportional to 21.15, 29.20 and 13.88 is: 19.17

Step by Step Solution

  1. Step 1: Write the proportion equation
    21.15 : 29.20 = 13.88 : x
  2. Step 2: Convert to fraction form
    21.15/29.20 = 13.88/x
  3. Step 3: Cross multiply
    21.15x = 29.20 × 13.88
  4. Step 4: Simplify right side
    21.15x = 405.30
  5. Step 5: Solve for x
    x = 405.30/21.15
  6. Step 6: Final answer
    x = 19.17

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Why These Related Problems?

These problems maintain the same ratio (1.38) or explore similar proportional relationships. Practicing with related ratios helps build understanding of proportional relationships.