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Finding the Fourth Proportional to 19.78, 29.70 and 13.80

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Solution

The fourth proportional to 19.78, 29.70 and 13.80 is: 20.72

Step by Step Solution

  1. Step 1: Write the proportion equation
    19.78 : 29.70 = 13.80 : x
  2. Step 2: Convert to fraction form
    19.78/29.70 = 13.80/x
  3. Step 3: Cross multiply
    19.78x = 29.70 × 13.80
  4. Step 4: Simplify right side
    19.78x = 409.86
  5. Step 5: Solve for x
    x = 409.86/19.78
  6. Step 6: Final answer
    x = 20.72

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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.