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Finding the Fourth Proportional to 19.21, 28.80 and 13.20

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Solution

The fourth proportional to 19.21, 28.80 and 13.20 is: 19.79

Step by Step Solution

  1. Step 1: Write the proportion equation
    19.21 : 28.80 = 13.20 : x
  2. Step 2: Convert to fraction form
    19.21/28.80 = 13.20/x
  3. Step 3: Cross multiply
    19.21x = 28.80 × 13.20
  4. Step 4: Simplify right side
    19.21x = 380.16
  5. Step 5: Solve for x
    x = 380.16/19.21
  6. Step 6: Final answer
    x = 19.79

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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.